1、
(1/5):x=(1/6):15
(1/6)x=(1/5)*15
(1/6)x=3
x=18
2、
5/4.8=(x/0.6):15
(x/0.6)*4.8=5*15
(x/0.6)*4.8=75
x/0.6=15.625
x=9.375