Вычеслите устно: и в столбик:)
28,8:9; 67,2:21;
25,8:6; 43,7:23;
63:5; 57,5:25

28.8 / 9 = 28 8/10 / 9/1 = 288/10 * 1/9 = 288/90 = 3 18/90 = 3 2/10 = 3.267.2 / 21 = 67 2/10 / 21/1 = 672/10 * 1/21 = 672/210 = 3 42/210 = 3 2/10 = 3.225.8 / 6 = 25 8/10 / 6/1 = 258/10 * 1/6 = 258/60 = 4 18/60 = 4 3/10 = 4.343.7 / 23 = 43 7/10 / 23/1 = 437/10 * 1/23 = 437/230 = 1 207/230 = 1 9/10 = 1.963 / 5 = 63/1 / 5/1 = 63/1 * 1/5 = 63/5 = 12 3/5 = 12.657.5 / 25 = 57 1/2 / 25/1 = 115/2 * 1/25 = 115/50 = 2 15/50 = 2 3/10 = 2.3