Bob buys two things in a shop. With his pocket calculator he calculates in advance what he has to pay: 5.25 dollars. But what he does not notice is that he pressed the division instead of the addition button. At the desk he is not surprised if he hears that he has to pay 5.25 dollars. What is the price of the two things Bob has bought?

Let us call the two prices of the things x and y.
According to Bob's (wrong) calculation: x / y = 5.25
According to the shop x + y = 5.25.
From the first equation it follows that x = 5.25*y. Pluggin this into the second equation gives that
6.25 * y = 5.25.
This gives y = 0.84 and x = 4.41.
So the things Bob has bought costed 0.84 and 4.41 dollars.