a). 3 + 2 + 5 = 5 + 5 = 10
3 × 2 × 5 = 6 × 5 = 30
10 < 30
b). 7 + 9 - 12 + 48 = 16 - 12 + 48 = 4 + 48 = 52
7 × 9 - 12 + 48 = 63 - 12 + 48 = 51 + 48 = 99
52 < 99
c). 48 : 6 : 2 = 8 : 2 = 4
48 - 6 - 2 = 42 - 2 = 40
4 < 40
d). 54 - 6 + 72 - 9 = 48 + 72 - 9 = 120 - 9 = 111
54 : 6 + 72 : 9 = 9 + 8 = 17
111 > 17