1. a) $7x - 3 = x + 3 \Rightarrow 6x = 6 \Rightarrow x = 1$
б) $\frac{2x-3}{4} = \frac{2}{3} \Rightarrow 3(2x-3) = 8 \Rightarrow 6x - 9 = 8 \Rightarrow 6x = 17 \Rightarrow x = \frac{17}{6}$

2. a) $\frac{15xy^4}{10x^3y^2} = \frac{3y^2}{2x^2}$
б) $\frac{ab-b}{b^2} = \frac{b(a-1)}{b^2} = \frac{a-1}{b}$

3. $(3a-2)(3a+2) - (3a+1)^2 = 9a^2 - 4 - (9a^2 + 6a + 1) = -6a - 5$.
При $a = \frac{1}{12}$: $-6 \cdot \frac{1}{12} - 5 = -\frac{1}{2} - 5 = -5.5$

4. a) $\frac{6^{15} \cdot 6^{11}}{6^{24}} = \frac{6^{26}}{6^{24}} = 6^2 = 36$
б) $\frac{(5^3)^5 \cdot 3^{16}}{9 \cdot 225^7} = \frac{5^{15} \cdot 3^{16}}{3^2 \cdot (15^2)^7} = \frac{5^{15} \cdot 3^{16}}{3^2 \cdot