a) $$5 \div \frac{4}{15} = 5 \cdot \frac{15}{4} = \frac{75}{4} = 18\frac{3}{4} = 18.75$$
б) $$2 \div \frac{8}{9} = 2 \cdot \frac{9}{8} = \frac{18}{8} = \frac{9}{4} = 2\frac{1}{4} = 2.25$$
в) $$131 \div \frac{64}{52} = 131 \cdot \frac{52}{64} = \frac{131 \cdot 13}{16} = \frac{1703}{16} = 106\frac{7}{16} = 106.4375$$
г) $$\frac{64}{125} \div 4 = \frac{64}{125} \cdot \frac{1}{4} = \frac{16}{125} = 0.128$$
д) $$9 \div \frac{3}{4} = 9 \cdot \frac{4}{3} = \frac{36}{3} = 12$$
е) $$9 \div 4 = \frac{9}{4} = 2\frac{1}{4} = 2.25$$
Ответ: а) 18.75; б) 2.25; в) 106.4375; г) 0.128; д) 12; е) 2.25