99 points + brainliest answer! i need with this! 9. solve the system by substitution. {-x – y – z = -8 {-4 + 4y + 5z = 7 {2x + 2z = 4

{-x – y – z = -8           (1)
{-4 + 4y + 5z = 7        (2)
{2x + 2z = 4               (3)

divide equation (3) by 2
x + z = 2 so z = 2 -x

substitute z = 2 -x into (1) 
-x – y – z = -8
-x - y - (2 -x) = -8
-x - y -2 + x = -8
-y = -6
 y = 6

-4 + 4y + 5(2 -x) = 7 
-4 + 4y + 10 - 5x = 7
6 + 4y - 5x = 7
4y - 5x  = 1                   
4(6) - 5x = 1
5x = 23
   x = 4.6

z = 2 - x
z = 2 - 4.6
z = -2.6

answer
   x = 4.6,  y = 6 and z = -2.6

Ralph is earning 2.8% commission