Temperature Question

This morning the temperature was 12 degrees celsius. by 12pm it had increased by 7 degrees so it is now 19 degrees celsius. by 6pm the temperture then dropped down by 5 degrees to be 14 Now at 8pm,it has dropped 3 more degrees,so the new temperture is 11 degrees celsiuis. 12 + 7 - 5 - 3 = 11