a,15+23+(-25)+(-23)=[ (-23)+23] +[(-25)+15] = 0+(-10)= -10
b,-23.63+23.21-58.23=23.(-63)+23.21-58.23=23.(-63+21-58)=23.(-100)=-2300
a)
15 + 23 + ( -25 ) + ( -23 )
= [ 15 + ( -25 ) ] + [ 23 + ( -23 ) ]
= -10 + 0
= -10.
b)
-23.63 + 23.21 - 58.23
= -23 . ( 63 - 21 + 58 )
= -23 . 100
= -2300.