Question

Substitution for 4x+y=9 and y=-7

Answer 1

4x + y = 9

y = -7

Plug it in:

4x - 7 = 9

Add 7 to both sides:

4x = 16

Divide 4 to both sides:

x = 4

Plug this back into the equation:

4x + y = 9

4(4) + y = 9

16 + y = 9

Subtract 16 to both sides:

y = -7

So our solution is (4, -7)

Answer 2

{y=-7

{4x+y=9 Substitute y.

4x+(-7)=9

4x-7=9 /+7

4x=16 /:4

x=4

Solution; (4; -7)