Instead of "a half", write "eight sixteenths". That doesn't change the value of any numbers, but it makes it a lot easier to subtract the three sixteenths from the eight sixteenths.
Half of one-fourth is one eight
two and one half
6 and 1/4
The answer is 1/4. There are 4 fourths in a whole. Convert 1/2 into 2/4, then subtract 1/4
three and one fourth
three eigths or 3/8