51.25×4/5-61.2×5/6+71又1/6÷7/6
=(50+5/4)×4/5-(60+6/5)×5/6+(70+7/6)×6/7
=50×4/5+5/4×4/5-60×5/6-6/5×5/6+70×6/7+7/6×6/7
=40+1-50-1+60+1
=(40+60-50)+(1-1+1)
=50+1
=51
[40又1/2-(18.75-1÷8/15)×2]÷27/40
=[40.5-(18.75-15/8)×2]×40/27
=[40.5-18.75×2+15/8×2]×40/27
=(40.5-37.5+3.75)×40/27
=(3+3.75)×40/27
=6.75×40/27
=27/4×40/27
=10