Question 1109554
<font face="Times New Roman" size="+2">


If the son is 15, then the father, who is 4 times as old, must be 60 years old.  Then the current sum of their ages is 15 + 60 = 75.  You must add 40 to 75 to get to 115.  Since 2 is added to the sum of their ages every year, it will take 20 years to increase the sum of their ages by 40.


John
*[tex \LARGE e^{i\pi}\ +\ 1\ =\ 0]
My calculator said it, I believe it, that settles it
<img src="http://c0rk.blogs.com/gr0undzer0/darwin-fish.jpg">
*[tex \Large \ \
*[tex \LARGE \ \ \ \ \ \ \ \ \ \  

</font>