So first you have to find the median, to do this you use the formula (n+1)/2 with n being how many numbers there are.
As there are 4 numbers we can substitute it into the formula to make (4+1)/2 which is 2.5
Then you find the 2nd place and the 3rd place (which are 5 and 8) and find exactly the middle of them which is 6.5 (the median)
To find the lower quartile we take the 2.5 from earlier and divide it by 2 to make 1.25 so we find where that place is in the number. 4 is the first place and then we find what 1/4 is and add that on to make 4.25 which is the lower quartile.
Then you do 2.5+1.25 to find the upper quartile to make 3.75 so we find where that is in the numbers which is in-between 8 and 13 so it will be 8+1.22 to make 9.22
So to find the interquartile range you do the upper quartile takeaway the lower quartile so 9.22-4.25 which is 4.97 and that is the answer
11 times with a remainder of 5
