a)1x(1+1)-(1-1):1 =1*2-0:1=2
b)[500-(3500:700x80-40x9)X(64:8)]:9-(72:6):(81:27)=
=[500-(5x80-40x9)×8]:9-12:3=[500-40×(5x2-9)×8]:9-4=(500-40×8):9-4=
=(500-320):9-4=180:9-4=20-4=16
m)2x{350:[491-3x(125-78)]+350} = 2x[350:(491-3x47)+350]=
=2x[350:(491-141)+350]=2x(350:350+350)=2×(1+350)=2×351=702