$a^3{b}^5\ast <!--\; \ast \; -->a^4{b}^7=a^{3+4}{b}^{5+7}=a^7{b}^{12}$

$c^4{d}^7\ast <!--\; \ast \; -->c^8{d}^3=c^{4+8}{d}^{7+3}=c^{12}{d}^{10}$

$m^9{n}^2\ast <!--\; \ast \; -->n^5{m}^3=m^{9+3}{n}^{2+5}=m^{12}{n}^7$

$p^2{q}^7\ast <!--\; \ast \; -->p^3{q}^6=p^{2+3}{q}^{7+6}=p^5{q}^{13}$