9.
a)
a = +175 - 23 - 34 = 152 - 34 = 118
b = -21 - 800 - 12 = - 833
a + b = 118 + (-833) = - 715
a - b = 118 - (-833) = 118 + 833 = 951
b)
a = +105 - 2073 = - 1968
b = - 157 - 812 = -969
a + b = - 1968 + (-969) = -2937
a - b = - 1968 - (-969) = - 1968 + 969 = 999
10.
a = [(-15+27)+(-13+29-16)+(+16+34+10)]-(-14+20)
= [12+(16-16)+(50+10)]-6
= (12+0+60)-6 = 72-6 = 66
b = [-35+(-21+7+24) - (15-30-89)+34]-(+73)
= [-35+(-14+24)-(-15-89)+34]-73
= (-35+10+104+34)-73
= (-25+104+34)-73
= (79+34)-73
= 113-73 = 40
c = [-15+(-25+89-4)-(-35)+127]
= [-15+(64-4)+35+127]
= -15+60+35+127
= 45+35+127 = 80+127 = 207
c > a > b
