a) 1/2+3/4 = 1/4+3/4 = 2/4+3/4 = 5/4
1/3+7/9 = 3/9+7/9 = 10/9
5/6+1 1/4 = 10/12+1 3/12 = 1 13/12
b) 1 3/5+2 4/15 = 1 9/15+2 4/15 = 3 13/15 = 4 2/15*
2 1/4+1 2/3 = 2 3/12+1 8/12 = 3 11/12 = 4 1/12
1 5/6+7/9 = 1 15/18+14/18 = 1 29/18
c) 7/10+4/5+1/2 = 7/10+8/10+5/10 = 20/10
3/4+5/7+1 1/2 = 21/28+20/28+1 14/28 = 1 62/28
