First make the fractions into decimals so it's easier to compare them.
1/2 ⇒ 0.5
2/3 ⇒ 0.66
2/5 ⇒ 0.4
3/4 ⇒ 0.75
Now it's easy to order the numbers from least to greatest.
First order the decimals.
0.4, 0.5, 0.66, 0.75
Now order them with their corresponding fractions.
2/5, 1/2, 2/3, 3/4 is your answer.