Answer
$\frac{3a}{20}$
Work Step by Step
The product of two or more fractions is the product of their numerators divided by the product of their denominators.
If $\frac{a}{b}$ and $\frac{c}{d}$ are fractions then,
$\frac{a}{b}$*$\frac{c}{d}$ = $\frac{a*c}{b*d}$
So according to the above statement
$\frac{3}{4}$*$\frac{a}{5}$ = $\frac{3*a}{4*5}$ = $\frac{3a}{20}$