[tex]a) \: {2}^{9} \div ( {6}^{7} \div {3}^{7} ) = {2}^{9} \div {2}^{7} = {2}^{2} = 4[/tex]
[tex]b) \: {125}^{7} \times 25 = ( {5}^{3} ) {}^{7} \times {5}^{2} = {5}^{21} \times {5}^{2} = {5}^{23} [/tex]
