a) 5/12-5/3+1/6-2/9
=5×3/12×3-5×12/3×12+1×6/6×6-2×4/9×4
=15/36-60/36+6/36-8/36
=15-5+6-8/36
=8/36
b) 2-1/3+1/6-1/9
=1/3+1/6-1/9
=1×6/3×6+1×3/6×3-1×2/9×2
=6/18+3/18-2/18
=6+3-2/18
=7/18
c)4/3-(1/2+7/8)
=4/3-(1×4/2×4+7/8)
=4/3-(4/8+7/8)
=4/3-(4+7/8)
=4/3-11/8
=4×8/3×8-11×3/8×3
=32/24-33/24
=32-33/24
=-1/24
d)4/3-7/5-(3/5-5/7)
=4/3-7/5-(3×7/5×7-5×5/7×5)
=4/3-7/5-(21/35-25/35)
=4/3-7/5-(21-25/35)
=4/3-7/5-(-4/35)
=4×35/3×35-7×21/5×21-(-4×3/35×3)
=140/105-147/105-(-12/105)
=140-147-(-12)/105
=5/105
