elmination

Question

9x+8y=-28

x-y=-5

Answer 1

9x + 8y = -28

x - y = -5

 

x = y - 5            add y to both sides of second equation

 

9(y - 5) + 8y = -28   substitute

9y - 45 + 8y = -28    distribute

17y - 45 = - 28         combine

17y = 17                  add 45 to both sides 

y = 1                        divide both sides by 17

 

You can determine the value of x.

 

Or

 

9x + 8y = -28
x - y = -5

 

9x + 8y = -28

9x - 9y = -45      multiply both sides of second by 9

 

17y = 17            subtract bottom from top

y = 1