4 1/9*0,9; 27,2*2/17; 2 1/3*1,2; 0,6:9/25; 8/21:0,5; 3,5:4 2/3.

1) 4 1/9 * 0,9 = (4 * 9 + 1) / 9 * 9/10 = 37/9 * 9/10 = (37 * 9) / (9 * 10) = 37/10;

2) 27,2 * 2/17 = 272/10 * 2/17 = (272 * 2) / (10 * 17) = (16 * 2) / 10 = 32/10;

3) 2 1/3 * 1,2 = (2 * 3 + 1) / 3 * 12/10 = 7/3 * 12/10 = (7 * 12) / (3 * 10) = 28/10;

4) 0,6 : 9/25 = 6/10 * 25/9 = (6 * 25) / (10 * 9) = 5/3;

5) 8/21 : 0,5 = 8/21 * 10/5 = (8 * 10) / (21 * 5) = 16/21;

6) 3,5 : 4 2/3 = 35/10 : (4 * 3 + 2) / 3 = 7/2 : 14/3 = 7/2 * 3/14 = (7 * 3) / (2 * 14) = 3/4.