3. Выполните действие: 1) (x+y)/5 − x/5; 2) 4m²/5 + m²/5; 3) 12/x² · x/3; 4) a²/3 : a/15.

1. \(\frac{x+y}{5}-\frac{x}{5}=\frac{x+y-x}{5}=\frac{y}{5}\).
2. \(\frac{4m^2}{5}+\frac{m^2}{5}=\frac{5m^2}{5}=m^2\).
3. \(\frac{12}{x^2}\cdot\frac{x}{3}=\frac{12x}{3x^2}=\frac{4}{x}\).
4. \(\frac{a^2}{3}:\frac{a}{15}=\frac{a^2}{3}\cdot\frac{15}{a}=5a\).

Ответ: 1) \(\frac{y}{5}\); 2) \(m^2\); 3) \(\frac{4}{x}\); 4) \(5a\).