If 12 types only last 4 days, and the rest last an average of 6, then the average amount of days that ALL the flowers wilt would be 5. To find the average, you add 6 and 4 to get 10, and since there is only 2 number we added togehter to get 10, you would divide 10 by 2 to get 5!
The y intercept, (0,400) represents the amount of money the radio station originally had. The x-intercept, (8,0), represents the amount of weeks it will take for the radio station to have $0 left.