2. Упростите: 1) \(2a^{-2}:\frac{2}{3}a\); 2) \(1{,}2x^{-2}:4x^{-5}\); 3) \(3m^{-2}n^3:\frac{3}{4}m^{-3}n^3\).

1. \(2a^{-2}:\left(\frac{2}{3}a\right)=\frac{2a^{-2}}{\frac{2}{3}a}=3a^{-3}=\frac{3}{a^3}\), при \(a\ne0\).
2. \(1{,}2x^{-2}:4x^{-5}=\frac{1{,}2}{4}x^{-2-(-5)}=0{,}3x^3\), при \(x\ne0\).
3. \(3m^{-2}n^3:\left(\frac{3}{4}m^{-3}n^3\right)=4m^{-2-(-3)}n^{3-3}=4m\), при \(m\ne0\) и \(n\ne0\).

Ответ: 1) \(\frac{3}{a^3}\); 2) \(0{,}3x^3\); 3) \(4m\).