If $\frac{3}{a}=4$, then find the value of $a$.

Given: $\frac{3}{a}=4$.

To do: To find the value of $a$.

Solution: 

Given $\frac{3}{a}=4$

$\Rightarrow \frac{3}{a}=\frac{4}{1}$

$\Rightarrow 3\times1=4\times a$                                       [On cross multiplication]

$\Rightarrow 4a=3$

$\Rightarrow a=\frac{3}{4}$

Therefore, $a=\frac{3}{4}$.