Question 1069140
The son is 7 years old and the daughter is 28 years old.

Let the son is X years old.
Then the daughter is 3*X years old.
The sum of all three persons ages in 10 years will be:
100 = X+10 + 3*X+10 + 42+10.
100 = 4*X + 10+10+42+10.
100 = 4*X +72.
4*X = 100-72 = 28.
X = 7.
3*X = 28.