1) 3/x + 3 = 7/15
Решение:
3/x = 7/15 - 3
3/x = 7/15 - 45/15
3/x = -38/15
x/3 = -15/38
x = -45/38

2) x - 5/20 = 6/7
Решение:
x = 6/7 + 5/20
x = 120/140 + 35/140
x = 155/140
x = 31/28

3) 5 3/5 : 3 1/4 : 2x
Решение:
5 3/5 : 3 1/4 : 2x
28/5 : 13/4 : 2x
112/20 : 65/20 : 2x
112 : 65 : 2x
112/65 = 2x/65
112 = 2x
x = 112/2
x = 56

4) 0,24 : 2 2/3 = (x - 0,06) : 1 7/9
Решение:
0.24 : 8/3 = (x - 0.06) : 16/9
0.24 3/8 = (x - 0.06) 9/16
0.09 = 9/16 (x - 0.06)
0.09 = 9x/16 - 9/16 0.06
0.09 = 9x/16 - 9/160
9/160 + 0.09 = 9x/16
9/160 + 9/100 = 9x/16
(9/160 + 9/100) * 160 = 9x
9 + 14.4 = 9x
23.4 = 9x
x = 23.4/9
x ≈ 2.6

5) 12.3/2.324 = x - 4/46.48
Решение:
12.3/2.324 = (x - 4)/46.48
5.29 = (x - 4)/46.48
5.29 * 46.48 = x - 4
245.99 = x - 4
x = 245.99 + 4
x = 249.99

Ответ: x = -45/38, x = 31/28, x = 56, x ≈ 2.6, x = 249.99