Explanation:
just think logically:
(2v/(v-7)) = x/((v-7)(v+9))
x = (2v/(v-7)) × (v-7)(v+9) = 2v(v-7)(v+9) / (v-7) =
= 2v(v+9) =
= 2v² + 18v
so, the blank is 2v(v+9) or 2v² + 18v.
both are the same, just the first is simplified, the second is the the result when doing the simplifying multiplication.