Решите уравнение: в) 3/7a + 2/5 = 1 и) 2/5z + 2/3z - 7/15z = 2 1/2

в) 3/7a + 2/5 = 1;

3/7а = 1 - 2/5;

3/7а = 5/5 - 2/5;

3/7а = 3/5;

а = 3/5 : 3/7;

а = 3/5 * 7/3;

а = 7/5 = 1 2/5.

Проверка:

3/7 * 7/5 + 2/5 = 1;

3/5 + 2/5 = 1;

1 = 1.

Ответ: а = 7/5 = 1 2/5.

и) 2/5z + 2/3z - 7/15z = 2 1/2;

6/15z + 10/15z  - 7/15z = 2 1/2;

16/15z - 7/15z = 5/2;

9/15z = 5/2;

3/5z = 5/2;

z = 5/2 : 3/5;

z = 5/2 * 5/3;

z = 25/6 = 4 1/6.

Проверка:

2/5 * 4 1/6 + 2/3 * 4 1/6 - 7/15 * 4 1/6 = 2 1/2;

2/5 * 25/6 + 2/3 * 25/6 - 7/15 * 25/6 = 5/2;

5/3 + 25/9 - 35/18 = 5/2;

30/18 + 50/18 - 35/18 = 5/2;

80/18 - 35/18 = 5/2;

45/18 = 5/2;

5/2 = 5/2.

Ответ: z = 25/6 = 4 1/6.