№1 Решите уравнение: 1) 6: x = 36: 30; 2) 12:7=3: x; 3) 4,9: 0,35 = x : 35; 4) \frac{x}{21} = \frac{9}{14}; 5): \frac{16}{90} = \frac{x}{42}; 6) \frac{108}{b} = \frac{3}{8}.

Ответ: 1) x = 5; 2) x = 1.75; 3) x = 49; 4) x = 13.5; 5) x = \frac{112}{45}; 6) b = 288

Решение уравнений:

1) 6 : x = 36 : 30 \[ \frac{6}{x} = \frac{36}{30} \] \[ x = \frac{6 \cdot 30}{36} = \frac{180}{36} = 5 \] 2) 12 : 7 = 3 : x \[ \frac{12}{7} = \frac{3}{x} \] \[ x = \frac{3 \cdot 7}{12} = \frac{21}{12} = 1.75 \] 3) 4.9 : 0.35 = x : 35 \[ \frac{4.9}{0.35} = \frac{x}{35} \] \[ x = \frac{4.9 \cdot 35}{0.35} = \frac{171.5}{0.35} = 490 \cdot \frac{1}{10} \cdot \frac{100}{35} = 49 \] 4) \(\frac{x}{21} = \frac{9}{14}\) \[ x = \frac{9 \cdot 21}{14} = \frac{189}{14} = 13.5 \] 5) \(\frac{16}{90} = \frac{x}{42}\) \[ x = \frac{16 \cdot 42}{90} = \frac{672}{90} = \frac{112}{15} \approx 7.47 \] 6) \(\frac{108}{b} = \frac{3}{8}\) \[ b = \frac{108 \cdot 8}{3} = \frac{864}{3} = 288 \]

Ответ: 1) x = 5; 2) x = 1.75; 3) x = 49; 4) x = 13.5; 5) x = \frac{112}{45}; 6) b = 288