Решите уравнения; b:25/6=4/7:20/21

b : 25/6 = 4/7 : 20/21 b * 6/25 = 4/7 * 21/20 b* 6/25 = 4*21/7*20 b * /25 = 1*3/1*5 b * 6/25 = 3/5 b = 3/5 : 6/25 b = 3/5 * 25/6 b = 3*25/5*6 b = 1*5/1*2 b = 5/2 проверка: 5/2 : 25/6 = 4/7 : 20/21 5/2 * 6/25 = 4/7 * 21/20 5*6 / 2*25 = 4*21 / 7*20 1*3 / 1*5 = 1*3 / 1*5 3/5 = 3/5