Question 22156
We don't know the dimensions of the 1st square so let it be length=x and width =x.  This square can accomodate x^2 of the "characters".  But 24 are left over
so there must be x^2+ 24 characters.

The 2nd square has had a row and a column added so its length=x+1 and its width =x+1.  This 2nd square can accomodate (x+1)^2 characters.  But there
are then 25 positions in the square that have no character. Thus the total
number of characters must be (x+1)^2-25.

Since there are the same number of characters described in the two scenarios
the following equation must apply:

    x^2 + 24 = (x+1)^2-25

Solve this equation for "x".
Then the number of characters is x^2+24 or (x+1)^2 -25.
Both give the same number if you have correctly solved for "x".

Good luck,
Cheers,
Stan H.