3/4:1/2,4/9:8/9,5/6:7/12,3:1/2,1:2/7,1:1/4,10/21:5,2/3:4,9/10:3,10 1/2:3 1/2,3 3/5:6 3/4

1) 3/4 : 1/2 = 3/4 * 2 = (3 * 2)/4 = (3 * 2)/(2 * 2) = 3/2 = 1 1/2;

2) 4/9 : 8/9 = 4/9 * 9/8 = (4 * 9)/(9 * 8)/(4 * 9)/(4 * 2 * 9) = 1/2;

3) 5/6 : 7/12 = 5/6 * 12/7 = (5 * 6 * 2)/(6 * 7) = 10/7 = 1 3/7;

4) 3 : 1/2 = 3 * 2 = 6;

5) 1 : 2/7 = 1 * 7/2 = 3 1/2;

6) 1 : 1/4 = 1 * 4/1 = 4;

7) 10/21 : 5 = 10/21 * 1/5 = (5 * 2)/(21 * 5) = 2/21;

8) 2/3 : 4 = 2/3 * 1/4 = (2 * 1)/(3 * 2 * 2) = 1/6;

9) 9/10 : 3 = 9/10 * 1/3 = (3 * 3)/(10 * 3) = 3/10;

10) 10 1/2 : 3 1/2 = (10 * 2 + 1)/2 : (3 * 2 + 1)/2 = 21/2 : 7/2 = 21/2 * 2/7 = (7 * 3 * 2)/(2 * 7) = 3;

11) 3 3/5 : 6 3/4 = (3 * 5 + 3)/5 : (6 * 4 + 3)/4 = 18/5 : 27/4 = 18/5 * 4/27 = (9 * 2 * 4)/(5 * 3 * 9) = 8/15.