Q is as much younger than R as he is older than T. If sum of the ages of R and T is 50 years, what is the difference between R and Q's age?

Let us assume Q age is Q years , R age is R years and T age is T years.
According to question,
Q is as much younger than R as he is older than T
Age of Q - T = R - Q
? Q = (R + T)/2
If sum of the ages of R and T is 50 years.
Hence, age of Q = 50/2 = 25 years
Here, absolute value of age of R is not known.
So the difference between R and Q's age cannot be determined. Hence, data is inadequate.