The mode is the number the occurs the most in the set, and as you can see 4 appears twice. The median is the number that lies in the middle of the set when put together from least to greatest. When you write it out it results in 2,4,4,8,9,10,12. As you can see the number 8 lies right in the middle, with three numbers on it's left and three numbers on it's right. Hope this helps :)
