My teacher angry to me

I never forgot a day in my life. The day is 'I made my teacher angry'. This story happened when I studied grade 7, the day that I studied about ' plus and minus point on strength line'.

At that time, teacher studied about 'plus and minus on strength line' than teacher drew a picture and she write something that I couldn't understand, She said that ' You look and I'll explain you later', than I've a look for 10 minutes and I said ' teacher I don't understand explain me.' I see a very strength line on the line have 4 point A;B;C; and D, after that I look down there are AB=????, AC=????, AD=???

I listened to my teacher but I still couldn't understood and She ask me' Understand?', first I want to said No, It's too messy but when I saw her face very hot and tired I said ' Yes! I understand it' but the thing I never thought is SHE CALLED ME TO DO EXERCISE, what could I do if I didn't understand anything?????? I just did it........... I held on pen for 15 minutes and I could do nothing, she shout to me 'I knew already you couldn't and Why you said you can do??? I heart your mother said you're clever but I can't where is you clever????' I scared my teacher >_<....... 'Come see this exercise what plus what or minus what equal [AB]??'.
'I don't know teacher' I said but I knew already that she will shout to me again. 'Just do it, when I explain you ? did you listen?? where is your ears?? You didn't bring your ears from home??' She shout to me and hit me and I said'[AB]=[A~C]-[AC]'. 'wrong' She said and hit me again "[AC]-[BC]' . 'OK! next'...........after 2 hour I've answer all the exercise. but teacher didn't say anything to me she walked very fast left the class and her face red and so angry'.

After that day, I always remember this lesson forever never forgot and I also never forgot the words teacher said to me at that day.. >_<