a) [6.8-10:(-5)+(-2)^2.(-7)]
= [48+2+4.(-7)]
=[48+2+(-28)]
= 22
b) 3.(-7)+[(-123):3-4.|-8|]
= -21+[-41-4. 8]
=-21 +[-41.32]
=-21+(-1312)
=-1333
c) -12+12.(-74)+12.(-25)
= 12.(-1) +12.(-74) +12. (-25)
=12.[-1+(-74)+(-25)]
=12. (-100)
= -1200
d) 23.(13-11)-13.(23-11)
= 23.13-23.11-13.23-13.11
= -23.11-13.11
= 11(-23-13)
= 11. (-36)
= -396