Pascal is 3 years older than Serge. The sum of their ages is 23. How old is each individual?

Pascal is 13 and Serge is 10

Step-by-step explanation:

Let Pascal's age be x

Then Serge is x - 3

Sum of their ages is 23

x + x - 3 = 232x - 3 = 232x = 26x = 13

Pascal is 13 and Serge is 10

-- Start a list.
-- At the beginning of the list, write zero. 
-- Next on the list, write ' 1 '.
-- Now you have the beginning of the Fibonacci series.
-- Whenever you want to add a new term to the list, sum up
     the last two terms on the list.  Their sum is the new term.