Question

How to work this problem

Answer 1

So in order to use the substitution method, you rearrange one to have a variable isolated, so i isolated y. Then you plug in and solve for the other variable, then plug in that to an equation to find the remaining variable.

Answer 2

7x + 9y = - 27_________eq1
3x - y = 3__________eq2
Multiply eq 2 by 9 and then add the resulting eq with eq1.

eq2 x 9 gives us   27x - 9y = 27___________eq3
 
add eq3 with eq1 we get.
34x = 0.
where x=0/34
x=0.
substitute x into any of the above equations to get y.
substitute x into eq1. we get:
7(0) + 9y =-27
9y = -27
y= -27/9
y = -3.