\(a,=28+19-28-32+57\\ =\left(28-28\right)+\left(19-32+57\right)\\ =0+44\\ =44\\ b,=39+13-26-62-39\\ =\left(39-39\right)+\left(13-26-62\right)\\ =0-75\\ =-75\\ c,=29+37+13+10-37-13\\ =\left(13-13\right)+\left(37-37\right)+\left(29+10\right)\\ =39\\ d,=-21-43-7-11+53+17\\ =\left(-21-11\right)+\left(-43+53\right)+\left(-7+17\right)\\ =-32+10+10\\ =-12\)
a,=28+19−28−32+57=(28−28)+(19−32+57)=0+44=44b,=39+13−26−62−39=(39−39)+(13−26−62)=0−75=−75c,=29+37+13+10−37−13=(13−13)+(37−37)+(29+10)=39d,=−21−43−7−11+53+17=(−21