Решите уравнение 12 : 4x/5 = 20 : 1/4

12 : 4x/5 = 20 : 1/4;

12 : 4x/5 = 20 * 4/1;

12 : 4x/5 = 80;

60 : 4х = 400;

4х = 60 : 400;

4х = 60/400 = 3/20;

х = 3/20 : 4;

х = 3/20 * 1/4;

х = 3/80.

Проверка:

12 : 4 * 3/80 : 1/5 = 20 : 1/4;

12 : 4*3/20/5 = 20 * 4/1;

60 : 4 * 3/80 = 400;

60 : 3/20 = 400;

60 * 20/3 = 400;

1200/3 = 400;

400 = 400.

Ответ: х = 3/80.