So it is really easy to solve firstly we can see how much does the first 10 boxes make which makes around 55$ obviously. Secondly 45$ for the next 10 boxes.
So for now we can simply calculate that we have spent around 100$ which means 20 boxes. The remaining money left is 77$ so we can buy 77/3.5 = 22 only 22 boxes with that money. Hence a total of 42 boxes.
The correct answer for this question is that the unit rate is 5:1. We
can work this out by simplifying down the 2 commercials to every 10
songs ration, so that 10:2 becomes 5:1. We can work this out by halving
the original ratio to simplify it.
Whats not affected by the
others outcome