Answer
(a) $-1$
(b) $(-1,\infty)$
(c) $ 25$
Work Step by Step
(a) Given $f(x)=log_3(x+2)$, we have $f(x)=0\longrightarrow log_3(x+2)=0 \longrightarrow x+2=3^0 \longrightarrow x=-1$
(b) $f(x)\gt0\longrightarrow log_3(x+2)\gt0 \longrightarrow x+2\gt3^0 \longrightarrow x\gt-1$ or $(-1,\infty)$
(c) $f(x)=3\longrightarrow log_3(x+2)=3 \longrightarrow x+2=3^3 \longrightarrow x=25$
