Question

Solve by substitution:
a+b=5
3a+4b=15

Answer 1

What do you want to solve for first, a or b?

Answer 2

I'll go with a

Answer 3

Ok, so we need to get b on one side. The first equation will probably be easiest to do this with.

Answer 4

so like: b=5a ?

Answer 5

Close, good try :) It would actually be b = 5 - a since we need to subtract a

Answer 6

alright

Answer 7

Now, substitute that in for b in the second equation.

Answer 8

3(5-a)+4b=15

Answer 9

That equation equals b, not a :)

Answer 10

okay 3(5-b)+4b=15 ...right?

Answer 11

3a + 4(5 - a) = 15

Answer 12

ohhh

Answer 13

3a+20-4a=15

Answer 14

Do you get why I put it in for b though?

Answer 15

yes i do

Answer 16

that is correct, now just solve for a

Answer 17

-1a=15-20

Answer 18

Yep, so -a = -5. Now we need to multiply the entire thing by -1 to get positive a

Answer 19

a=5

Answer 20

Yes! Now we can substitute in 5 for a in either of the equations and get b

Answer 21

I can't tell if it's easier to plug it into the 1st equation or the 2nd

Answer 22

The first probably, all that is in the first is just subtracting from both sides

Answer 23

okay so 5+b=5
bring 5 to the other side....
5-5=0

Answer 24

b=0

Answer 25

so therefore the poi is (5,0)

Answer 26

@sleepyjess thanks for the help!

Answer 27

yep, that is correct, sorry, was afk for a little bit :)