Question

I need help substituting number 4.

Answer 1

       Solve, for the first variable in one of the equation, the substitute the final result into the other equation 
 
 
- $\frac{17}{3}$  ;  - $-\frac{211}{21}$ 

Answer 2

I solved for x first by substituting y into equation # 2. 

-4y - 30 = -6x    =   -4y = -6x+30   =   y = (6x-30)/4

25 = -7y + 8x    

 25 = -7(6x-30)/4 + 8x

25 = (-42x + 210)/4 + 8x

25 = -10.5x + 52.5 + 8x

-27.5 = -2.5x

x = 11

Now solve for y

-4y - 30 = -6x

-4y - 30 = -66

-4y = -36

y = 9

Plug both numbers into the equations above and your answer checks out.

-4(9) - 30 = -6(11)

-36 - 30 = -66 (True)

25 = -7y + 8x

25 = -7(9) + 8(11)

25 = -63 + 88 (True)

hope this helps unless I totally misunderstood what the question was (which happens)