This has been around for years but, just in case you'd forgotten, typing a calculation in the Google search box will give you the answer. Even better is just typing the sum in the address bar in Google Chrome where the answer comes up without you even having to go the trouble of hitting Return!
I used to have the Windows Calculator pinned to the Start menu but that can go now. (It always struck me as odd that it was buried in Accessories, Notepad, too. Hmm maybe I can find something else for that too.)
Lastly, whilst on the topic of old stuff that's still useful, I am still amazed at how swiftly IrfanView opens up and does the job of editing and saving images like screenprints. The two illustrations above were so easy. Where no special effects or pixel work are required this free programme is quite brilliant and long may it remain light and simple.