mean is the average; so you would take all of the numbers, add them up, then divide by how many numbers there are. so
112+113+116+116+116+116+118+118+119+119+124+124+124=1419.
now since there are 12 numbers we would do 1419/12=118.25 (or 473/4)
median is the middle; so you would put all the numbers in order from highest to lowest and find the middle number. if there are two you add them then divide by 2.
so in this case both 118’s are in the middle. 118+118=236. 236/2=118