Question 253939
a mother who is 40 years old has a 10 year old daughter. In how many years will the mother be three times as old as the daughter?
You may edit the question. Maybe convert formulae 

Let x be the number of years when the mother's age  will be 3 times the daughters.

Then:

40 + x = (10 + x) * 3

40 + x = 30 + 3x  
2x = 10
X = 5