1/4 + 1/2 + 0.5 = 0.25 + 0.5 + 0.5 = 1.25

7/15 + 2.8 = 0.46 + 2.8 = 3.26

3 17/20 - 2.7 = 3 + 17/20 - 2.7 = 3 + 0.85 - 2.7 = 3.15 - 2.7 = 0.45