First you would put the numbers in order, but this problem already has them set up like that.
22.5, 23, 24, 25.5, 27.5, 29, 32, 33.5, 35
To find the minimum and maximum, just look at the highest and lowest numbers in the data set. In this case, there are 22.5 for the minimum and 35 for the maximum.
The median is the middle of the data set. In this case it has an exact number stated of 27.5. Sometimes you have to find the middle of the two numbers in the middle if the data set has an even amount of numbers.
To find the quartile 1 and 3, find the middle of the numbers that are NOT the median. Q1 is the lower, and Q3 is the higher. Q1 would be 23.5, the middle of 23 and 24. Q3 would be 32.75.
To find the IQR or Inter-Quartile Range, do this: Q3-Q1. The answer for this problem is 9.25.
Sorry this was a bit long. Let me know if you are still having trouble. I hope this helps.