решите уравнения; b:25/6=4/7:20/21

b : 25/6 = 4/7 : 20/21b * 6/25 = 4/7 * 21/20b* 6/25 = 4*21/7*20b * /25 = 1*3/1*5b * 6/25 = 3/5 b = 3/5 : 6/25b = 3/5 * 25/6b = 3*25/5*6b = 1*5/1*2b = 5/2проверка:5/2 : 25/6 = 4/7 : 20/215/2 * 6/25 = 4/7 * 21/205*6 / 2*25 = 4*21 / 7*201*3 / 1*5 = 1*3 / 1*53/5 = 3/5