No, the side length 7,8 and 15 can not form a triangle because i have the formula for this which: a+b greater than c, but 7 plus 8 is not greater than 15.
Next, i need to order the number which is: 1,3,4,6,9,11, so the quartile 1 is 3 and quartile 3 is 9, so the interquartile range is 6. Hope it help!