Which value of x satisfies both -9x + 4y = 8 and -3x - y = 4 given the same value of y?

Question

the options are

A)-1/7
B)-7/9

C)-9

D)-4/3

Answer 1

From -9x + 4y = 8

         4y = 9x + 8

         y = (9x + 8)/4

 

From -3x - y = 4

         y = -3x - 4

 

Since y has the same value in both equations:

 

y = (9x + 8)/4 = -3x - 4

 9x + 8 = 4(-3x - 4) = -12x -16

21x = -24

x = -8/7

 

y = -3x - 4 = 24/7 - 4 = -4/7

 

This is the answer even though there it is not one of the listed options.