So, we know the perimeter is 24 cm. and the top part is the left part, (x) + 2, but remember, we need to have it be a number that, multiplied by 2, is 24. So, using this formula, the length, (top / bottom) is 7, and x = 5. Because 5 + 5 = 10, and when length is +2, it adds up to 14. 10 + 14 = 24. So, length is 7, width, (left, right) is 5.
I put 40 (Number of birthday cards bought previously) over 125 (Number of expected costumers) and multiplied it by 100 (Total number of card bought previously) to get my answer. Hopefully that helps :)
