Question 1083702
 Jake is 52 years old.
 How old is joe if Jake is now twice as old as joe was when Jake was as old as joe is now?
:
Jake's age = 52
let j = Joe's age
let d = 52 - j; the difference in their ages
"How old is joe if Jake is now twice as old as joe was when Jake was as old as joe is now?"
52 = 2(j - d)
52 = 2j - 2d
Replace d with (52 - j) 
52 = 2j - 2(52-j)
52 = 2j - 104 + 2j
52 = 2j + 2j - 104
52 + 104 = 4j
156 = 4j
j = 156/4
j = 39 yrs is Joe's present age