1) -1/24 - (1/4 - (1/2 - 7/8))
=-1/24 - (1/4 - 1/2 + 7/8)
=-1/24 - 1/4 + 1/2 - 7/8
=-1/24 - 6/24 + 12/24 - 21/24
=(-1 - 6 + 12 - 21)/24
=-16/24
=-2/3
b) 1/2 + 1/6 + 1/12+ 1/20 + .....+ 1/9900
=(1/2 + 1/9900)
=4950/9900 + 1/9900
=(4950 + 1)/9900
=4956/9900