How to add, subtract, multiply, or divide in Excel? 在Excel裡如何加減乘除?

Today my mum asked me how to add, subtract, multiply and divide in Microsoft Excel, because she was setting up a spreadsheet for her job.
今天我媽問我如何在Excel裡加減乘除，因為她在工作上需要。

(on a side note, add/subtract/multiply/divide in English about 8 syllables, translated into Chinese is only 4 syllables "Jia Jian Cheng Chu".. much easier to say)
(加減乘除四個字，中文比英文好講多了)

So I showed her a video I made for Youtube a while ago. I hadn't looked at it for a while, it now has 11,000 views.
我給她看了一個我做的Youtube影片。已經一陣子沒看了，現在突然察覺到有一萬一千多播放次數。

My mum watched it for a while and then fully understood what to do. She said it was a great video, and that I spoke very clearly.
我媽看了一下就會了。她說這影片很好，我講話很清晰。

I'm glad I'm helping people through the internet.
很高興我能夠在網路上幫助別人。