2/3 - 1/6 = (2 × 2 - 1 × 1)/6 = 4/9 - 1/6 = 3/6 = 1/2
4/5 + 1/2 = (4 × 2 + 1 × 5)/10 = 8/10 + 5/10 = 13/10 = 1 3/10
2/15 + 9/40 = (2 × 8 + 9 × 3)/120 = 16/120 + 27/120 = 43/120
7/16 - 3/8 = (7 × 1 - 3 × 2)/16 = 7/16 - 6/16 = 1/16
7/20 - 7/32 = (7 × 8 - 7 × 5)/160 = 56/160 - 35/160 = 21/160
1/36 + 5/24 = (1 × 2 + 5 × 3)/72 = 2/72 + 15/72 = 17/72