Explanation:
with the starting definition of PT = TQ we know that T is the midpoint between P and Q.
that means there is the same distance between P and T as between T and Q.
14a.
the answer is already above
PT = TQ = 5
14b.
since T is the midpoint, its distance to the endpoints P and Q is half of the overran distance bergen P and Q.
PQ = 2×5 = 10