0.7 1.4 1.8 2.2 3.9
Look first of all at the units place. The choices are 0 1 2 and 3
the 0 place is going to come first. Then the 1s (both of them) and the 2 and then 3.
Now look at the tenths place. The two where that matters is 1.4 and 1.8.
1.4 < 1.8 so the order is 1.4 followed by 1.8