Question 763344
x is son's age now.  Father is now 36.  If you subtract x from 36 for Father, then subtract x from son's x age when son was born, age 0.  


when_______Father__________Son
Now________36______________x
SonBorn____36-x___________x-x=0


Father was {{{36-x=x}}} when son was born, when son's age was 0.


{{{36=2x}}} because add x to both sides
{{{2x=36}}}
{{{highlight(x=18)}}}___________ANSWER