Question

Erica solved the equation −5x − 25 = 78; her work is shown below. Identify the error and where it was made.

−5x − 25 = 78
Step 1: −5x − 25 − 25 = 78 − 25
Step 2: −5x = 53
Step 3: negative five times x over negative five = fifty-three over negative five
Step 4: x = negative fifty-three over five

Step 1: She should have added 25 to each side.
Step 1: She should have divided both sides by −5.
Step 3: She should have divided both sides by −5.
Step 3: She should have multiplied both sides by −5.

Answer 1

Any idea?

Answer 2

no

Answer 3

i am not good at this

Answer 4

are you still here

Answer 5

Well when you're doing algebra the goal is to isolate a certain variable for these kinds of questions (meaning get x on its own) and to do this you usually do the opposite operation to move it to the other side, so for example if we have:

2x-3=45
our first step would be get move the -3 to the right side but what you do to one side you must do also do to the other.
so add +3 on both sides and you can see it will get cancelled on the left
2x-3+3=45+3
2x=48
now you're left with 2x, you see "2x" is stuck together they are being multiplied, so we say ok what's the opposite operation that will remove the 2, oh right division! Divide both sides by 2 and you'll get x = 24

Answer 6

Read that over, and see if you can figure it out, try your best and take your time and get back to me, it's ok if you get it wrong, or don't get a specific part, just ask.

Answer 7

but what is the answer step one ore three please

Answer 8

Well I want you to figure it out, I see you got rid of 2 answers which were wrong, so good job, can you get rid of 1 more?

Answer 9

-5x-25=78 say this was a test, what would be your first step to isolate x, look at the example I gave you.

Answer 10

is the first of step 3

Answer 11

negative five times x over negative five = fifty-three over negative five , this?

Answer 12

Are you sure James?

Answer 13

nvm

Answer 14

It's actually in my example if you just go over it

Answer 15

the second of step 1

Answer 16

I'm not sure what that means, are you saying step 1 is where the error is, where Erica was subtracting -25 instead of adding?

Answer 17

yes

Answer 18

Yup, you're absolutely correct! :)

Answer 19

thank you so much

Answer 20

thank you

Answer 21

i need help with one more plz