4.a. -50
b. 1100
c. 4
d.200
e.10
f.0
g.0
h.-20
5. a, (91+9)+(19-18)=100+1=101
c. (-46-54)-(999+1)=-100-1000=-1100
b.245-245-(375+25)=0-400=-400
d.77+3-(1+99)=100-100=0
