x:3.25=1/5:5/4
x:13/4=1/5:5/4
x=(13/4)*(1/5)*(4/5)
x=13/25
检验:(13/25)*(4/13)=4/25
(1/5)*(4/5)=4/25
经检验可知x=13/25是原式子的正解