.
This problem is for MENTAL solution.
Since the sum of their ages will be 37 six years from now, the sum of their ages now is 12 years less than 37, i.e. 37 - 12 = 25.
Thus you have that the sum of their ages is 25, while Rachel is 5 years older than Haline.
Then it is obvious that Haline is 10 years old, while Rachel is 15 years old.
Solved.