Answer:
14
Step-by-step explanation:
An isosceles triangle has two sides that are the same. If one side is 7 and another is 14, then the two possibilities are 7, 7, and 14, or 14, 14, and 7.
It can't be 7, 7, and 14, because the sum of the shortest sides of a triangle must be greater than the longest side.
Therefore, it must be 14, 14, and 7. So the third leg is 14.