(7分之1减9分之1)×63
=1/7×63-1/9×63
=9-7
=2
8分之3×5分之1+8分之5×5分之1
=（3/8+5/8）×1/5
=1/5
6分之5÷3分之4﹢6分之5×4分之3
=5/6×3/4×2
=5/8×2
=5/4
7分之3×11分之9－11分之2÷3分之7
=3/7×（9/11-2/11）
=3/7×7/11
=3/11