Ask your own question, for FREE!
Mathematics 24 Online
iosangel:

can someone walk me through this I don't understand this equation at all

iosangel:

3/x+5=8/x+2

Hero:

Is it ONE: \(\dfrac{3}{x} + 5 = \dfrac{8}{x} + 2\) or TWO: \(\dfrac{3}{x + 5} = \dfrac{8}{x + 2}\)?

iosangel:

two

Hero:

Okay, so going forward, next time you have an equation like that write it this way using parentheses: 3/(x + 5) = 8/(x + 2)

iosangel:

ok

Hero:

Anyways, to solve it, you have to do what is called cross multiplication. Anytime you have two ratios equated to each other: \(\dfrac{a}{b} = \dfrac{c}{d}\) you cross multiply to get \(ad = bc\)

Hero:

In this case you would cross multiply to get \(3(x + 2) = 8(x + 5)\) Are you able to solve for \(x\) from here?

iosangel:

No

Hero:

Do you know how to apply the distributive property here? \(a(b + c) = ab + ac\)

iosangel:

yes

Hero:

Okay, try doing that on both sides. Let me know what you get.

Hero:

We have a drawing tool btw just in case you didn't know: |dw:1567613363451:dw|

iosangel:

3*x=3x 3*2=6 8*x=8x 8*5=40 3x+6=8x+40

iosangel:

Im not sure if that right

Hero:

Did you apply the distributive property to 3(x + 5) = 8(x + 2)? I think you applied the distributive property incorrectly. You should write it linearly.

iosangel:

I got 3x+6=8x+40

Hero:

Sorry that's not right. You multiplied the wrong numbers you need to start over from here but write horizontally. 3(x + 5) = 8(x + 2)

iosangel:

what i know is that i multiply 3 *x then 3*5 right?

Hero:

Correct

iosangel:

Then i gtt 3x+15

Hero:

And what do you get for the other expression?

iosangel:

8x+16

Hero:

Very good. Now continue solving for x

iosangel:

3x+15=8x+16 8x-3x+15=8x+16-8x 5x+15=16 Like this?

Hero:

Looks right. Continue solving for x

Hero:

Hang on a minute. What have you done?

Hero:

Somehow you've managed to mix things up again.

Hero:

You need to subtract the same thing from both sides per line.

iosangel:

ok for 8x+16-8x ive crossed out the 8x and left me with 16 and 8x-3x+1 i solved and got 5x+15

Hero:

You'll need to start over again from 3x + 15 = 8x + 16

iosangel:

ok

Hero:

You have to subtract the same thing from both sides PER LINE. You cannot subtract 3x on one side then 8x on the other side.

iosangel:

here i subtract 8x from both sides right?

Hero:

You have to subtract 3x on BOTH sides

iosangel:

ok

iosangel:

but why not 8x?

iosangel:

will that be for later?

Hero:

Let's do one thing at a time. Subtract 3x on both sides. Then we'll go from there.

iosangel:

ok 3x + 15-3x = 8x + 16-3x 3x will be crossed out and leaves with 15 then 8x+16-3x=5x+16= so i got `15=5x+16

Hero:

And what are you going to do next?

iosangel:

subtract 16?

iosangel:

from both sides

Hero:

Exactly

iosangel:

ok 15-16=5x+16-16 -1=5x

Hero:

There's only one step left. Do you know what it is?

iosangel:

divide

Hero:

Divide what?

iosangel:

divide 5

iosangel:

both sides

iosangel:

then i gotx= -1/5

Hero:

Correct.

iosangel:

Ok thank you

Hero:

Now you have to check it

iosangel:

oh

iosangel:

idk how to do that tbh

Hero:

Plug the -1/5 back into the x of the original equation then evaluate both sides.

iosangel:

to both x?

Hero:

Correct

Hero:

If it is correct you should end up with the same value on both sides.

iosangel:

ok

iosangel:

3/(-1/5+5) =8/(-1/5+2)

iosangel:

Lol i got it wrong

Hero:

How do you figure?

iosangel:

i think it was 34/5

Hero:

What are you referring to?

iosangel:

i was supposed to multiply x+5 from both sides instead of doing distributive property thing im not sure.

Hero:

Can you post a screenshot of the original problem?

iosangel:

Ok

Hero:

Like from the book

iosangel:

It was a practice problem from a recording from my teacher

iosangel:

Ill show you how she wrote it

iosangel:

|dw:1567616162779:dw|

Hero:

That's not what you wrote originally

Hero:

Ah I see. I'm the one who made the mistake.

Hero:

It was 3(x + 2) = 8(x + 5)

Hero:

What matters though is knowing how to do the steps.

iosangel:

yes

Hero:

Consider what we did as an example

iosangel:

ok

Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!
Can't find your answer? Make a FREE account and ask your own questions, OR help others and earn volunteer hours!

Join our real-time social learning platform and learn together with your friends!