What fractions in this list are less than 1/2? 3/6,7/15,4/9,5/8

All we need to do is to find a common denominator for both 1/2 and the other numbers individually:

1/2 = 3/6 (so 3/6 is not less than 1/2 - both numbers are equal)
1/2 = 15/30 and 7/15 = 14/30 (so 7/15 is less than 1/2)
1/2 = 9/18 and 4/9 = 8/18 (so 4/9 is less than 1/2)
1/2 = 4/8 (so 5/8 is not less - it's greater than 1/2)

From the list above only 7/15 and 4/9 are less than 1/2.