(1)X/6=5/12
X:6 =5:12
12X =6×5
X=5/2
(2) 1/3:1/4=1/6:X
1/3X =1/4×1/6
X=1/8
(3)X:0.9=2.7:1.8
1.8X =0.9×2.7
X=1.35