What is the interquartile range of the data set?

key: 1|5 means 15

The graph below shows the amount of money left in the school’s desk fund, f, after d desks have been purchased. for each new desk that is purchased, by how much does the amount of money left in the school’s desk fund decrease?

Let r = 3. what is the value of r + 58?

I’m really confused and need to learn this