Call the two dimensions A and B. One of these will match the 12-ft length of existing fence, so we can add in the existing fence to make the perimeter 44+12=56 feet=2(A+B). Therefore A+B=28 feet. We already know that one of these is 12 feet long, so the other is 28-12=16 feet, which is longer than 12 feet, so is the longer dimension.