如果x>1,那么÷x ; 如果x<1,那么÷x .
÷12==0.75= : = 折= %
12÷ =0.25= %= :24== (填成数)
9÷ == :8= (填小数)
20: = ÷20==0.8= %
==36÷ = (填小数)