Calculează:
a) 3+3×[3+3×(3+3×3)]:15
b) 812-4×[6×(61-3500:12:30)]:9
c) [214+240:(16-2×5)]×25-25:25
d) 90+7×[1614-12000: (18-10)]-16
e) 44+8×[280:(37-1480:20:37)]:32-7
f) (18×8+56) :[50×40:(220-2×60)]​