So Paula sold 2/5 of her tickets initially. Of the "remaining" tickets (remainder is the key word here) she gave 2/5 to her friend. So this means after selling her tickets she had 3/5 left, which she further divided by giving her friend 2/5 of the remaining 3/5. (Hope I'm making sense so far) so what that means is, you need to figure out how many tickets were given to her friend by dividing 72/3 equaling 24. This tells you what value every 1/5 of tickets she gave her friend are. So you multiply 24•5 (the whole) giving you a product of 120. 120 is how many tickets she had left after selling. Now you divide 120/3 (the tickets not sold) giving you a quotient of 40. 40 represents the value of 1/5 tickets, so to find the original sum of tickets you would multiply 40•5 equaling to 200 tickets in total. Hope that drawn out explanation made sense!
The reason for this answer is algebra. Since you give a full explanantion on it I'm not sure if I answered it correctly. But here is what I think from what you gave of the question.
