1) -5.2 - (2.6 - 5.2) = 5.2 -2.6 + 5.2 = 7.8
2) 7.4 - (2.4 + 5.5) = 7.4 - 2.4 - 5.5 = -0.5
4) (3.31 + 5.29) - (3.29 - 2.69) = 8.6 - 3.29 + 2.69 = 8
5) (4 1/2 + 7 2/7) - (5.5 + 4 1/7) = (9/2 + 51/7) - (55/10 + 29/8) = (63/14 + 102/14) - (220/40 + 145/40) = 165/14 - 365/40 = 3300/280 - 2555/280 = 745/280