Answer
$a^{\frac{1}{3}}$
Work Step by Step
Step 1: Since both the radicands multiply together, their indexes add to each other.
Step 2: Denoting the missing exponent by $x$,
$\frac{3}{3}=\frac{2}{3}+x$
Step 3: Therefore, x = $\frac{3}{3}-\frac{2}{3}$ = $\frac{1}{3}$
Step 4: The missing expression is thus $a^{\frac{1}{3}}$
