a, ( -18 + 25 ) - ( 125 - 18 + 25 )
= -18+25-125+18-25
= (-18+18) +(25-25) -125
= 0+0-125
= -125
b, 45 . ( 18 - 15 ) -18 . ( 45 + 45 )
= 45.18 - 45.15 -18.45 +18.45
= 45(18-15-18+18)
= 45.3=135
a ) = -18 + 25 - 125 + 18 - 25
= (-18 + 18 ) - ( 25 -25 ) + 125
= 0 - 0 + 125
=125