q = unknown number
9q + 6
[Six more(addition) than the product(multiplication) of nine and a number(q).
So 6 is added to 9q(9 times q).]
Since you know q = 6, substitue/plug it into the equation:
9q + 6 Plug in 6 into "q" since q = 6
9(6) + 6
54 + 6
60