7分之1÷14分之3-8分之5×5分之2
=1/7×14/3-5/8×2/5
=14/21-1/4
=56/84-21/84
=5/12
3分之2÷（5-3分之5）×6分之5
=2/3÷(15/3-5/3)×5/6
=2/3÷10/3×5/6
=2/3×3/10×5/6
=1/6