Задания из ОГЭ. Помогите с 4 и 7 пж )

4) $\frac{12}{x+5} = - \frac{12}{5}$
$\frac{-12}{5} = -2,4$
$\frac{12+2,4(x+5)}{x+5} = 0$
x≠-5
12 + 2,4x + 12 = 0
2,4x = -24
x = -10
Ответ:-10

7) $\frac{ a^{2}-25 b^{2} }{5ab} : (\frac{a-5b}{5ab}) = \frac{ (a^{2}-25 b^{2})(5ab) }{5ab(a-5b)} = \frac{ (a-5b)(a+5b) }{(a-5b)} = a+5b$
a = 8,0625
b = 6,1875
a+5b = 8,0625 + 5*6,1875 = 39
Ответ:39