Упростить..............

А)
$\frac{ {a}^{2} - {b}^{2} }{5 {a}^{2} } \times \frac{a}{3a + 3b} = \frac{(a - b)(a + b)}{5a} \times \frac{1}{3(a + b)} = \frac{(a - b)}{5a} \times \frac{1}{3} = \frac{a - b}{15a}$
б)
$\frac{x + a}{a} \div \frac{ax + {x}^{2} }{ {a}^{2} } = \frac{x + a}{a} \times \frac{ {a}^{2} }{ax + {x}^{2} } = (x + a) \times \frac{a}{x(a + x)} = \frac{a}{x}$
в)
$\frac{ \sqrt{15} }{ \sqrt{6} \times \sqrt{10} } = \frac{ \sqrt{15} }{ \sqrt{60} } = \frac{1}{ \sqrt{4} } = \frac{1}{2} = 0.5$