a, -(-238)+|-2017|+(-138)-17
=238+2017-138-17
=(238-138)+(2017-17)
=100+2000
=2100
b, (-3)³.8²+(-6)².(-27)
=-27.64+36.(-27)
=-27.(64+36)
=-27.100
=-2700
c, [-120+(200-465)-(265+|-100|+20)]:(-5)
=[-120+200-465-265-100-20]:(-5)
=[(-120-20)+(200-100)+(-465-265)]:(-5)
=[-140+100-730]:(-5)
=-770:(-5)
=154