Răspuns:
[tex] {5}^{13} \times {5}^{15} \div ( {5}^{4} ) ^{7} = {5}^{13 + 15} \div {5}^{4 \times 7} = {5}^{28} \div {5}^{28} = {5}^{28 - 28} = {5}^{0} = 1[/tex]