a ) - 24 + 13 + 6 +24
= [(-24) + 24 ] + 13 + 6
= 0 + 13 + 6
= 19
b) 28 + (-6) - 50 + 6
= 22 - 56
= - 34
c) - 27 + ( -789 ) + ( -73 ) +789
= [ (-789) + 789 ] + [ ( - 27 ) + ( -73) ]
= 0 + (-100)
= -100
d) (-23) + ( - 17 ) + 50 +(-10)
= [ ( -23 ) + ( -17 ) + ( -10) ] + 50
= ( -50 ) + 50
= 0
e) 1998+ (-72) + ( -1998 ) + 72
= [ 1998 + ( -1998 ) ] + [ (-72) + 72 ]
= 0 + 0
= 0