[tex]5 {}^{17} \div {5}^{9} = {5}^{8} [/tex]
[tex] {3}^{21} \div {3}^{18} = {3}^{3} [/tex]
[tex] {2}^{34} \div {2}^{30} = {2}^{4} [/tex]
[tex] {4}^{15} \div {2}^{26} = ( {2}^{2}) {}^{15} \div {2}^{26} = {2}^{30} \div {2}^{26} = {2}^{4} [/tex]
[tex] {25}^{8} \div {125}^{5} = ( {5}^{2} ) {}^{8} \div ( {5}^{3} ) {}^{5} = {5}^{16} \div {5}^{15} = {5}^{1} [/tex]
[tex] {16}^{9} \div {8}^{12} = ( {4}^{2}) {}^{9} \div ( {2}^{3} ) {}^{12} = {4}^{18} \div {2}^{36} = ( {2}^{2} ) {}^{18} \div {2}^{36} = {2}^{36} \div {2}^{36} = {2}^{0} [/tex]
Succes !