Question 790469
Assume Sandy is x years old now. Then her son would be x-25 years old. 
Since Sandy's present age is 7 years less than three times her son's present age, we have x+7=3*(x-25) => x+7=3x-75 => 2x=82 => x=41

So Sandy is 41 years old.

Check answer: Her son is 41-25=16 years old. 16*3=48, 48-8=41. Correct