Respuesta :

[tex]\bf 3^x=81\qquad \begin{cases} 81=3\cdot 3\cdot 3\cdot 3\\ \qquad 3^4 \end{cases}\implies 3^x=3^4\implies x=4[/tex]

if their base is the same, the exponents must also be the same for the equation to be true.