84 : (2 * 6) = (84 : 2) : 6 = 42 : 6 = 7
210 : (7 * 6) = (210 : 7) : 6 = 30 : 6 = 5
400 : (10 * 8) = (400 : 10) : 8 = 40 : 8 = 5