$9^{x+2}$ x $3^{5}$ =($9^{3}$ )$^{7}$
=$9^{x+2}$ x $3^{5}$ = $9^{21}$
=$9^{x+2}$ x $3^{5}$ = ($3^{2}$)$^{21}$
=$9^{x+2}$ x $3^{5}$ = $3^{42}$
=$9^{x+2}$=$3^{42}$ : $3^{5}$
=$9^{x+2}$=$3^{37}$
=[($3^{2}$)$^{x+2}$]=$3^{37}$
=$3^{2(x+2)}$ =$3^{37}$
=> 2(x+2)=37
x+2=37:2
x+2=18,5
x=18,5-2
x=16,5