Представьте в виде дроби

A)
$\frac{3x-1}{x^2} + \frac{x-9}{3x} = \frac{3(3x-1) + x(x-9)}{3x^2} = \frac{9x-3+x^2-9x}{3x^2} = \frac{x^2-3}{3x^2}$

б)
$\frac{5}{c+5} - \frac{5c-2}{c^2+3c} = \frac{5}{c+5} - \frac{5c-2}{c(c+3)} = \frac{5c(c+3) -(5c-2)(c+5) }{c(c+3)(c+5)} = \\ \\ = \frac{5c^2+15c - (5c^2+25c- 2c-10)}{c(c+3)(c+5)} = \frac{5c^2+15c -5c^2-23c+10}{c(c+3)(c+5)} = \\ \\ = \frac{10-8c}{c(c^2+8c+15)} = \frac{10-8c}{c^3+8c^2+15c}$