SOLUTION: using the substitution method.. what is the solution of the system? 8x+7y=31 -2x+y=17

Algebra ->  Linear-equations -> SOLUTION: using the substitution method.. what is the solution of the system? 8x+7y=31 -2x+y=17      Log On


   

Question 320253: using the substitution method.. what is the solution of the system?
8x+7y=31
-2x+y=17
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
using the substitution method.. what is the solution of the system?
8x + 7y = 31
-2x + y = 17
:
The 2nd equation is a good one to use for substitution
-2x + y = 17
add 2x to both sides
y = 2x + 17
:
In the first equation substitute (2x+17) for y, find x
8x + 7(2x+17) = 31
8x + 14x + 119 = 31
22x = 31 - 119
22x = -88
x = -88%2F22
x = -4
:
Find y
y = 2x + 17
y = 2(-4) + 17
y = -8 + 17
y = 9
:
:
Check solution in the original 1st equation
8x + 7y = 31
8(-4) + 7(9) = 31
-32 + 63 = 31