1) Г

[tex] \frac{14 {a}^{5} }{ {b}^{6} } \times \frac{b {}^{5} }{56 {a}^{4} } = \frac{a}{4b} [/tex]

2) Б

[tex] - \frac{ {a}^{2} b}{12c} \div \frac{ {ab}^{2} }{4c} = - \frac{ {a}^{2}b \times 4c }{12c \times {ab}^{2} } = - \frac{a}{3b} [/tex]

3) Д

[tex]( - \frac{2 {a}^{5} }{b {}^{4} } ) {}^{3} = - \frac{2 {}^{3}a {}^{5 \times 3} }{ {b}^{4 \times 3} } = - \frac{8 {a}^{15} }{ {b}^{12} } [/tex]

4) А

[tex] \frac{2ab - b {}^{2} }{9a} \times \frac{3a}{b} = \frac{b(2a - b)}{3b} = \frac{2a - b}{3} [/tex]