Answer:
14 years
Explanation:
Let X be the age of Mo's daughter today.
Mo's age today is 4X.
In 7 years, Mo's age will be 4X+7 and his daughter's age will be X+7.
Thus, Mo's age will be triple his daughter's age in 7 years if 3(X+7)=4X+7.
Solving this equation for X, we find that X=7.
Therefore, Mo's daughter is 7 years old today.
Mo's age today is 4*7=28 years.
In 7 years, Mo's age will be 28+7=35 years and his daughter's age will be 7+7=14 years.
Thus, Mo's age will be double his daughter's age in 14 years from today.
The answer is therefore 14 years.