Find the value of $ab$ $$5^a = 16, 8^b = 25$$


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*Find the value of $ab$. 


So, this question seems simple to solve. However, the most important thing is to know where to start. That's why I couldn't solve this problem. I've been looking for a method/strategy to solve all kinda questions which involve exponential terms. 
Now, rewriting the inequalities. 
$$5^a = 16 \implies 5^a = 4^2 \implies 5^a = 2^4$$
$$8^b = 25 \implies 8^b = 5^2  \implies 2^{3b} = 5^2$$
Or what about giving letters like $k$, $t$ or somewhat?
Regards!

Note that $5^a = 16$ so that $5^{\frac{3a}{4}}=8$ since $16^3 = 8^4$. But then $8^b = 5^{\frac{3ab}{4}} = 25$, so that $\frac{3ab}{4} = 2$, or $ab=8/3$.  
