Help with spreadsheet functions

I want to assign a function to a field that shows the sum of all my bills, and each time i check off an item, it's value is deducted from the sum. What is the appropriate fx code for this action? I'm new to creating/ using spreadsheets and I'm trying to use the numbers app on my iPhone to create a spreadsheet to track my bills due. It is a simple sum checklist with items, the amount due, and a checkbox beside each item.

Do you think Walmart will have the iPhone X?

Walmart is having a Black Friday sale with a $300 gift card with activation. I don't want to fight the crowd if it's unlikely they'll have them lol. I've asked some people there and they can't tell my anything.

Is there any difference between the beats wireless studio 2 and the brand new studio 3 wireless headphones?

I currently have the beats pro that I bought a few years ago and I have the new iPhone 8 and it doesn't take a headphone jack unless you buy the special adapter which isn't godly expensive like $5-7. But to me that defeats the purpose of the phone. I was just curious as to if there are any key differences between the two and if so, what are they? Which would you prefer the two? Or maybe even keeping my headphones and getting the adapter?

How can I overcome shyness

Whenever I post one picture of my selfie on facebook, Instagram I let it sit there for few minutes- literally am panicking behind my iPhone as my heart races, chaotic iris movement, can't think straight and even almost having a seizure in my bed…
You know, I'm very self conscious. I was 300 pounds when I was 10 the traumatize of people making fun of me hadn't left me since. In my head I'm totally over thinking beyond imagination.
'Oh my God what if they call me fat, blah blah blah' people back then even adults made fun of my size… I'm 130 something pounds today…
The shyness of my appearance really gets on my nerves… How to overcome it? I want to be one of those confident people someday…