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

a-1/7
b-7/9
c-8/7
d-9
e-4/3

C

Step-by-step explanation:

Since y will have same value, y doesn't really matter. Thus,

We can solve for y in the 2nd equation as:

-3x - y = 4

-3x - 4 = y

Now we can plug it into the first and solve for x:

-9x + 4y = 8

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

-9x - 12x - 16 = 8

-21x = 8 + 16

-21x = 24

x = 24/-21

x = -8/7

Correct answer is C.

Option C

C-8/7

Step-by-step explanation:

We have the following equations

  and

We want to find a value of x that satisfies both equations and obtains the same value of y.

To find the value of x, clear the value of y in both equations

------------------------------

Now solve both equations and solve for x.

The answer is