已知1999×△+4×□=9991,其中△, □是自然数,那么□= .
15÷ =62.5%= :16== (小数)
= ÷25=40%= :45.
24: == ÷1.2= 折=75%
= ×=36÷ = :13.5.
÷20=0.4= %=2: .