Use ⇧⇧ (macOS), or Shift+Shift (Windows/Linux) and then type in your sum. The result will appear at the top of the Search Everywhere dialog as Result:.
Perform basic calculations with Search Everywhere
Use ⇧⇧ (macOS), or Shift+Shift (Windows/Linux) and then type in your sum. The result will appear at the top of the Search Everywhere dialog as Result:.