The built-in in the Home menu of Excel went missing for me.
I could not find them to add back in.
I eventually got there...
Right click on ribbon [Customize the ribbon...]
In right most box under the words "Customize the Ribbon (i)"
The drop down box read "Main Tabs"
Below it in the tree view for "Main Tabs" I left clicked on "Home"
Having done that I clicked on the "Reset \/" button below
Then I selected "Reset only selected Ribbon Tab"
Then I clicked "OK"
I could now see the "Built-in Styles" of Bad;Good;Neutral;Calculation etc.