Решите пропорцию (53–58): а) x/2 = 3/7; б) x/3 = 2/5; в) x/12 = 7/10; г) x/16 = 9/32; а) 7/8 = x/6; б) 13/15 = x/10; в) 12/21 = x/14; г) 48/5 = x/34; а) 15/x = 5/8; б) 24/x = 8/7; в) 12/x = 4/5; г) 25/x = 5/7; а) 3/5 = 7/x; б) 8/7 = 15/x; в) 7/1 = 12/x; г) 8/1 = 3/x.

Находим неизвестный член пропорции, перемножая известные члены крест-накрест.

1. а) \(\dfrac{x}{2}=\dfrac{3}{7}\); \(7x=6\); \(x=\dfrac{6}{7}\).
2. б) \(\dfrac{x}{3}=\dfrac{2}{5}\); \(5x=6\); \(x=\dfrac{6}{5}\).
3. в) \(\dfrac{x}{12}=\dfrac{7}{10}\); \(10x=84\); \(x=\dfrac{42}{5}\).
4. г) \(\dfrac{x}{16}=\dfrac{9}{32}\); \(32x=144\); \(x=\dfrac{9}{2}\).
5. а) \(\dfrac{7}{8}=\dfrac{x}{6}\); \(8x=42\); \(x=\dfrac{21}{4}\).
6. б) \(\dfrac{13}{15}=\dfrac{x}{10}\); \(15x=130\); \(x=\dfrac{26}{3}\).
7. в) \(\dfrac{12}{21}=\dfrac{x}{14}\); \(21x=168\); \(x=8\).
8. г) \(\dfrac{48}{5}=\dfrac{x}{34}\); \(5x=1632\); \(x=\dfrac{1632}{5}\).
9. а) \(\dfrac{15}{x}=\dfrac{5}{8}\); \(5x=120\); \(x=24\).
10. б) \(\dfrac{24}{x}=\dfrac{8}{7}\); \(8x=168\); \(x=21\).
11. в) \(\dfrac{12}{x}=\dfrac{4}{5}\); \(4x=60\); \(x=15\).
12. г) \(\dfrac{25}{x}=\dfrac{5}{7}\); \(5x=175\); \(x=35\).
13. а) \(\dfrac{3}{5}=\dfrac{7}{x}\); \(3x=35\); \(x=\dfrac{35}{3}\).
14. б) \(\dfrac{8}{7}=\dfrac{15}{x}\); \(8x=105\); \(x=\dfrac{105}{8}\).
15. в) \(\dfrac{7}{1}=\dfrac{12}{x}\); \(7x=12\); \(x=\dfrac{12}{7}\).
16. г) \(\dfrac{8}{1}=\dfrac{3}{x}\); \(8x=3\); \(x=\dfrac{3}{8}\).