The solution is:
1/2 - 4/11
Get their LCD (least common denominator) which is 22.
For 1/2, divide its denominator by 22, and you'll get 11. Multiply it to 1 and you'll get a fraction of 11/22.
Next for 4/11, divide its denominator by 22 and you'll get 2. Multiply it to 4 and get a fraction of 8/22.
Since they have the same denominators you can simply subtract both fractions:
11/22 - 8/22 = 3/22 :)