12/25÷2÷3/5 = 12/25 *1/2 *5/3 =6/25*5/3=2/5（1/4*8/15+4）/(4/5) = (2/15+4)*5/4=2/15*5/4+4*5/4=1/6+5=5又1/63/2:4/5 =3/2*5/4=15/833/5:22 =33/5*1/22=3/101.5:51/2 =3/2*2/51=1/171.125:1/80=1又1/8*80=9/8*...