1) 1/2 + 1/4 = 2/4 + 1/4 = 3/4
2) 1/3 - 1/6 = 2/6 - 1/6 = 1/6
3) 1/4 + 1/8 = 2/8 + 1/8 = 3/8
4) 1/5 - 1/10 = 2/10 - 1/10 = 1/10