11) $$\frac{a}{2} + \frac{a-5}{3} =$$ 12) $$\frac{3}{x(x+5)} \cdot \frac{2(x+5)}{x} =$$ 13) $$\frac{2}{a-2} + \frac{2}{a} =$$ 14) $$\frac{6y+1}{2x} : \frac{1}{x} =$$ 15) $$\frac{b+2}{b^2-9} - \frac{b}{9-b^2} = $$

Решим данные примеры: 11) $$\frac{a}{2} + \frac{a-5}{3} = \frac{3a + 2(a-5)}{6} = \frac{3a + 2a - 10}{6} = \frac{5a - 10}{6} = \frac{5(a-2)}{6}$$. 12) $$\frac{3}{x(x+5)} \cdot \frac{2(x+5)}{x} = \frac{3 \cdot 2(x+5)}{x(x+5) \cdot x} = \frac{6(x+5)}{x^2(x+5)} = \frac{6}{x^2}$$. 13) $$\frac{2}{a-2} + \frac{2}{a} = \frac{2a + 2(a-2)}{a(a-2)} = \frac{2a + 2a - 4}{a(a-2)} = \frac{4a - 4}{a(a-2)} = \frac{4(a-1)}{a(a-2)}$$. 14) $$\frac{6y+1}{2x} : \frac{1}{x} = \frac{6y+1}{2x} \cdot \frac{x}{1} = \frac{(6y+1)x}{2x} = \frac{6y+1}{2}$$. 15) $$\frac{b+2}{b^2-9} - \frac{b}{9-b^2} = \frac{b+2}{b^2-9} + \frac{b}{b^2-9} = \frac{b+2+b}{b^2-9} = \frac{2b+2}{b^2-9} = \frac{2(b+1)}{(b-3)(b+3)}$$.