Пожалуйста,помогите!

1. $a=12, c=-2\\\frac{a + 3c}{c} = \frac{a}{c} + 3 = -6 + 3 = -3$

2. $\frac{2x-6}{x+2}\\ x+2\neq0 \\x \neq -2$

x ∈ (-∞; -2) ∪ (-2; ∞)

3. $\frac{6a - 5}{a^3} - \frac{2a -5}{a^3} = \frac{6a - 2a - 5 + 5}{a^3} = \frac{4a}{a^3} = \frac{4}{a^2}$

4. $\frac{2x + 6y}{5a - 5b}:\frac{3x + 9y}{7a - 7b} = \frac{2(x + 3y) * 7(a - b)}{5(a-b)*3(x + 3y)} = \frac{14}{15}$

5. $\frac{16b}{20b^4} = \frac{4b * 4}{4b * 5b^3} = \frac{4}{5b^3}$