The expression is equal to $\displaystyle{{5}}^{{-{{3}}}}\cdot{{3}}^{{2}}\usepackage{cmbright}\Huge\$ . The negative in the first exponent does not apply to the factor $\displaystyle{{3}}^{{2}}\usepackage{cmbright}\Huge\$ . It does not go into the denominator. After you simplify the two factors, remember that to multiply two fractions, you multiply the numerators and you multiply the denominators.