Greetings! Lets solve this problem shall we!?
If the merchant sold 24 cases of tapes which was 20% of what he or she had left, then 80% of the tapes were still in stock! So the question is how many tapes are still in stock?
If 24 cases of tapes is 20% out of 100%, then 96 cases are in the other stock.
Finally, there are 5 parts of (20%) = 100% so 5(24 cases) = 120 total cases.
Im not sure what you are asking in the question here but I hope this helps!