Question

Найдите неизвестный член пропорции 1) x:20=2:5; 2)x:18=7:9; 3)x:18=2:3; 4) 6:x=3:7; 5) 5:9=15:x; 6) 12:7=60:x;

Answer 1

х/20=2/5
5х=20×2
5х=40
х=40:5
х=8

х/18=7/9
9х=18×7
9х=126
х=126:9
х=14

х/18=2/3
3х=18×2
3х=36
х=36:3
х=12

6/х=3/7
3х=7×6
3х=42
х=42:3
х=14

5/9=15/х
5х=15×9
5х=135
х=135:5
х=27

12/7=60/х
12х=60×7
12х=420
х=420:12
х=35

Answer 2

1)
$\frac{x}{20} = \frac{2}{5} \\ \frac{20 \times 2}{5} = 8$
2)
$\frac{x}{18} = \frac{7}{9} \\ \frac{18 \times 7}{9} = 14$
3)
$\frac{x}{18} = \frac{2}{3} \\ \frac{18 \times 2}{3} = 12$
4)
$\frac{6}{x} = \frac{3}{7} \\ \frac{6 \times 7}{3} = 14$
5)
$\frac{5}{9} = \frac{15}{x} \\ \frac{9 \times 15}{5} = 27$
6)
$\frac{12}{7} = \frac{60}{x} \\ \frac{7 \times 60}{12} = 35$