Question 573622
Minh is 16
His parents are each X years old.


If we add their ages, we get 100 yrs old. 
100 = 16 + X + X  
100 = 16 + 2X  subtracting 16 from each side:
84 = 2X   dividing each side by 2:
42 = X


Each of Minh's parents is 42 yrs old.