Question 1132151

Bon wants to take an early retirement in 10 years when he will be twice as old as his daughter Sonia. Sonia is 25 years younger than her father. how old is Bon now? How old will he be when he retires? (use only one variable)(thanks in advance)
<pre>The father will be twice his daughter's age when the daughter reaches the age the father was when she was born.
That time is in 10 years, when the daughter will be 25, and the father, 2(25), or 50 years-old.
As the above event will be in 10 years' time, the father is now 50 - 10, or 40 years-old

Since you state that you need only 1 variable used, then we do the following:
Let Bon's age be B
Then his daughter's age is B - 25
We then get: B + 10 = 2(B - 25 + 10)______B + 10 = 2(B - 15)_____B + 10 = 2B - 30
B - 2B = - 30 - 10
- B = - 40
B, or Bon is: {{{highlight_green(matrix(1,4, (- 40)/(- 1), "=", 40, years-old))}}}
Can you now find out what his age will be in 10 years' time? You should be! I told you before!