a)[(-30):(+10)-(-8)x(+5)]:(-1) =
[ - 3 - ( - 40)] : ( -1 ) =
(- 3 + 40) : ( - 1) =
37 : ( - 1 ) =
- 37
b)[(-175):(-25)-(-42):(-14)]x[(-25)x(+3)-(-30)x(-3)]=
(7 - 3) × ( - 75 - 90) =
4 × ( - 165) =
- 660
c)-15x{(-72):[(-8)x(+3)-(+40):(-4)+50]+(-18)x(-2):(-6)}
- 15 ×{(-72):[ -24 - (-10) + 50] + 36 : ( -6) } =
- 15 ×[ - 72: ( - 24 + 10 + 50) - 6] =
- 15 × ( - 72 : 36 - 6) =
- 15 × ( - 2 - 6) =
- 15 × ( - 8) =
120
