Answer
$x=1$
Work Step by Step
Use the law of exponents ($b^n\times b^m=b^{n+m}$) to add the exponents together. Then rewrite $81$ to have base $3$. With the bases equal, set the exponents equal to each other and solve.
$3^{x+2}\times3^{x}=81$
$3^{2x+2}=81$
$3^{2x+2}=3^4$
$2x+2=4$
$2x=2$
$x=1$
