a, 40+46.85+15.46
=40+(46.85+15.46)
=40+46.(85+15)
=40+46.100
=40+4600
=4640
b, 2007+2^2:(3^2-7)
=2007+4:(9-7)
=2007+4:2
=2007+2
=2009
c, 75+[(-15)+(-10)]+(-50)
=75+(-25)+(-50)
=75+(-75)
=0
d, 280-[80-(10-6)^2]
=280-[80-4^2]
=280-[80-16]
=280-64
=216
mk nhanh nhất k cho mk nha bn
chúc bn học giỏi
thanks very much