a) The sum of your ages is F + (F+B) = 2F+B.
b) In 3 years, the sum of your ages will be (F+3)+(F+B+3) = 2F+B+6.
c) The difference of your ages at any time is B.
Instead of adding more fraction strips you would take some away to get a smaller number.
3 was gold 15 left bronze is twice of silver then bronze is 10 medals