Which of the ordered pairs in the form (x, y) is a solution of this equation? 5x-y/3 = 13 (2, -9), (3, -6)
a. the first is not a solution, but the second is.
b. neither is a solution.
c. the first is a solution, but the second is not.
d. both are solutions.

C. The first is a solution, but the second is not.

5x - y/3 = 13 ; (2,-9)
substitute the letters:
5(2) - (-9/3) = 13 
10 - (-3) = 13 : note that deducting a number with a negative sign turns both sign as positive.
10 + 3 = 13 ;
13 = 13

5x - y/3 = 13 ; (3,-6)
5(3) - (-6/3) = 13
15 - (-2) = 13
15 + 2 = 13
17 = 13 not equal. not a solution