Explicação passo-a-passo:

[tex] \frac{ {x}^{2}y }{4} \: . \: xy \: . \: 8y = [/tex]

[tex] \frac{8 {x}^{3} {y}^{3} }{4} = [/tex]

[tex]2 {x}^{3} {y}^{3} [/tex]

[tex] = = = = = = = = = = = = = = [/tex]

[tex] \frac{2ac}{3} \: . \: ( - \frac{5 {a}^{2} }{2}) \: . \: ( - \frac{a {b}^{3} }{4}) = [/tex]

[tex] \frac{10 {a}^{4} {b}^{3}c }{24} = [/tex]

[tex] \frac{5 {a}^{4} {b}^{3}c }{12} [/tex]

[tex] = = = = = = = = = = = = = = [/tex]

[tex]( - 4ab) \: . \: {a}^{9} \: . \: (2ac) \: . \: (abc) = [/tex]

[tex] - 8 {a}^{12} {b}^{2} {c}^{2} [/tex]