122. Решите уравнения: a) x/12 - 5 = x/18; б) x/14 = 15 - x/21; г) x/20 = -7 + x/25.

Решение:

• а) x/12 - 5 = x/18
1. x/12 - x/18 = 5
2. 3x/36 - 2x/36 = 5
3. x/36 = 5
4. x = 5 * 36
5. x = 180
• б) x/14 = 15 - x/21
1. x/14 + x/21 = 15
2. 3x/42 + 2x/42 = 15
3. 5x/42 = 15
4. 5x = 15 * 42
5. 5x = 630
6. x = 630 / 5
7. x = 126
• г) x/20 = -7 + x/25
1. x/20 - x/25 = -7
2. 5x/100 - 4x/100 = -7
3. x/100 = -7
4. x = -7 * 100
5. x = -700

Ответ: а) 180; б) 126; г) -700.