8y + 5x = -7
     8y = -7 - 5x
      =  - x
      y =  - x

(b) Find three solutions of the equation.

Substitute x = 2

      y =  - (2)
      y =  - 
      y = 

So one solution is (2,) and we've ruled out the third and fourth
answer.  There is no need to substitute x = 4 because y =  is the
same in the first three answers.  So:      

substitute x = 6

      y =  - (6)
      y =  - 
      y = 

So another solution is (2,).  So the first answer
is the correct one.

Edwin