$\displaystyle \log_a(3)=q$ & $\displaystyle \log_a(2)=p$ Express $log_a 72$ in terms of p & q $\displaystyle \log_a(3)=q$ & $\displaystyle \log_a(2)=p$ Express $log_a 72$ in terms of p & q
Currently I have tried nothing as I cannot even figure out where to begin a demonstration kindly will help much 
Many thanks :)

Observe the following rules of logarithm:
$$ \log_n ab = \log_n a + \log_n b$$
$$ \log_n a^b =b\log_n a $$
First you need to simplify the logarithms by factoring 72 into multiples of 2 and 3:
\begin{align} \log_a 72 &= \log_a (2^3 \times 3^2) \\ &= \log_a2^3 + \log_a 3^2\\ &= 3\log_a 2 + 2\log_a3\\ &= 3p + 2q\end{align}
