二分之一×[20-(二分之九-四分之一÷25%)]
=1/2*[20-(9/2-1/4*4)]
=1/2*[20-(9/2-1)]
=1/2*[20-7/2]
=1/2*33/2
=33/4
三又二十分之七÷[五又四分之三-4.5×(20%+三分之一)]
=67/20÷[23/4-4.5×(1/5+1/3)]
=67/20÷[23/4-9/2×8/15]
=67/20÷[23/4-12/5]
=67/20÷67/20
=67/20*20/67
=1
二分之一×[20-(二分之九-四分之一÷25%)]
=1/2*[20-(9/2-1/4*4)]
=1/2*[20-(9/2-1)]
=1/2*[20-7/2]
=1/2*33/2
=33/4
三又二十分之七÷[五又四分之三-4.5×(20%+三分之一)]
=67/20÷[23/4-4.5×(1/5+1/3)]
=67/20÷[23/4-9/2×8/15]
=67/20÷[23/4-12/5]
=67/20÷67/20
=67/20*20/67
=1