20-（2分之1+3分之1）除以6分之5*1.2 4分之1+5又7分之2*4分之1+3有7分之5除以4

20-（2分之1+3分之1）除以6分之5*1.2*4分之1+5又7分之2*4分之1+3有7分之5除以4
20-(1/2+1/3)/(5/6)*1.2*1/4+5又(2/7)*(1/4)+3又(5/7)/4
=20-(3/6+2/6)/(5/6)*0.3+(37/7)*(1/4)+(26/7)/4
=20-(5/6)*(6/5)*0.3+(37/28)+(26/28)
=20-0.3+(37+26)/28
=19.7+63/28
=197/10+63/28
=2758/140+315/140
=3073/140
=21又(133/140)
8.8*1.25*100/4
=8.8*1.25*25
=11*25
=275
(4/9)*[3/4-(7/16-0.25)]
=(4/9)*[3/4-(7/16-1/4)]
=(4/9)*[3/4-(7/16-4/16)]
=(4/9)*[3/4-(3/16)]
=(4/9)*[12/16-(3/16)]
=(4/9)*(9/16)
=1/4