Write each age as a variable (or as a multiple of x when a ratio is given), translate each statement into an equation, and remember that the difference between two people's ages never changes.
1Translating statements
Present age x ⇒ n years ago: x − n, after n years: x + n
Ratio a : b ⇒ ages ax and bx
'A is k times as old as B' ⇒ A = kB