Answer
$0$
Work Step by Step
Given : $(3x^{3}y^{a})^{3}=27x^{9}$
(The empty square box is represented as $a$)
Hence, $3^{3}$ X $x^{9}$ X $y^{3a}=27x^{9}$
(since $(ab)^{n} = a^{n}b^{n}$ and $(a^{m})^{n}=a^{mn})$
This becomes : $27$ X $x^{9}$ X $y^{3a}$ = $27$ X $x^{9}$ X $y^{0}$
($3^{3} = 27$ and $y^{0} = 1$)
This implies : $y^{3a}$ = $y^{0}$
Thus, $3a=0$ and $a=\frac{0}{3}=0$
Final result : $0$
