2. Найдите значение выражения \(\frac{6a+7b}{3a-4b}\), если: 1) \(a=20,\ b=12\); 2) \(a=10{,}8,\ b=6\); 3) \(a=2{,}4,\ b=0{,}8\); 4) \(a=12,\ b=5{,}6\).

1. \(\frac{6\cdot20+7\cdot12}{3\cdot20-4\cdot12}=\frac{120+84}{60-48}=\frac{204}{12}=17\).
2. \(\frac{6\cdot10.8+7\cdot6}{3\cdot10.8-4\cdot6}=\frac{64.8+42}{32.4-24}=\frac{106.8}{8.4}=12.714285\ldots=\frac{89}{7}\).
3. \(\frac{6\cdot2.4+7\cdot0.8}{3\cdot2.4-4\cdot0.8}=\frac{14.4+5.6}{7.2-3.2}=\frac{20}{4}=5\).
4. \(\frac{6\cdot12+7\cdot5.6}{3\cdot12-4\cdot5.6}=\frac{72+39.2}{36-22.4}=\frac{111.2}{13.6}=\frac{139}{17}\).

Ответ: 1) 17; 2) \(\frac{89}{7}\); 3) 5; 4) \(\frac{139}{17}\).