Answer
$p=1$ and $q=-1$
Work Step by Step
Dimension of t: [T]
Dimension of v: $\frac{[L]}{[T]}$
Dimension of a: $\frac{[L]}{[T]^{2}}$
$a=v^{p}t^{q}$
$\frac{[L]}{[T]^{2}}=(\frac{[L]}{[T]})^{p}([T])^{q}$
$[L]^{1}\times[T]^{-2}=[L]^{p}\times[T]^{q-p}$
$p=1$
$q-p=-2$
$q-1=-2$
$q=-1$