Explanation:
bring both fractions to the same denominator (bottom number). then we can readily compare our add or subtract them.
what is the snaked common multiple of 2 and 3 (the smallest number that can be divided without remainder by both numbers)?
it is 6 (in case of doubt simply multiply both numbers and use the result as common denominator).
so, we need to bring both to fractions in the form .../6.
2/3 = 4/6
1/2 = 3/6
so,
4/6 - 3/6 = 1/6
and that is the answer to the original question.