I am stuck in the question, please help me. Explain in clear formatting.

5) You want to know if an octopus (octopi are very intelligent!) can tell the difference between circles and rectangles. You provide each octopus with one circular disk and one flattened rectangle. You hide food under the circle. After several trials, you then count how many times the octopus picks up the circle and how many times it picks up the rectangle. You get the following results: Circles: 18 Rectangles: 4 Can the octopus tell the difference between circles and rectangles? (Hint: if the octopus can't tell the difference, what's the probability that he/she will pick a circle?)