a. (42-98)-(42-12)-12= 42-98-42+12-12
= (42-42) + (12-12) -98
= 0-98 = -98
b. (-5).4.(-2).3.(-25) = [(-5).(-2)] . [(-25).4] . 3
= 10. (-100) .3
= -1000 .3 = -3000
c. (-8).25.(-2).4.(-5).125 = [(-8).125] . (25.4). [(-2).(-5)]
= - 1000 . 100. 10
= -1000000
d. 19.25+9.95+19.30= 19.25+9.5.19+19.30
= 19. ( 25+45+30)
= 19. 100 = 1900