So, first determine what half of the denominator or bottom number would be.
Half of 13 would be 6.5 (Do 13 divided by 2).
Next, see if the numerator or top number on the fraction is smaller, the same, or bigger than that number.
Since 6.5 is bigger than 6, the numerator would be smaller.
If it is smaller, keep the whole number (in this case 12) the same. If it is the same or equal, round up (in this case 13).
Since 6 is smaller than 6.5, you keep 12 the same.
Your answer would be 12.
Hope this helped!