Question

Solve the system (using substitution) x - 2y = -7 and 3x + 4y = -6. The y-value of the solution is:

Answer 1

when solving by substitution we want to get a value for one variable in "terms" of the other.

x-2y = -7
x = -7 +2y well use this for our value of "x" in the other equation.

3x +4y = -6

3(-7 +2y) + 4y = -6

-21 +6y +4y = -6

10y = -6+21

10y = 15

y = 15/10 = 1.5

the value of y should be 1.5 if I kept my wits about me :)

better double check myself tho..

Answer 2

x = -7 +2(1.5)

x = -7 + 3

x=-4

-4 - 2(1.5) = -7
-4 -3 = -7 ..good there

3x + 4y = -6
3(-4) + 4(1.5) = -6

-12 +6 = -6
-6 = -6 ....its all good :)

Answer 3

Does that make sense to you?

Answer 4

Yes. That helped a lot. Thank you