A: (3/4 - 11/8) / (5/3 - 7/6)
=(6/8-11/8)/(10/6-7/6)
=(-5/8)/(3/6)
=-5/8*6/3
=-5/8*2
=-10/8
=-5/4
B: (1/4 - 1/5) / (1/5 - 1/6)
=(5/20-4/20)/(6/30-5/30)
=(1/20)/(1/30)
=1/20*30
=30/20
=3/2
C: 2/3 - (-4/9 + 7/6)
=2/3-(-8/18+21/18)
=2/3-(13/18)
=12/18-13/18
=-1/18
D: (8/7-6/5) * 7/4 -2
=(40/35-42/35)*7/4-2
=-2/35*7/4-2
=-7/70-2
=-1/10-20/10
=-21/10