Something wrong with some numbers in that spreadsheet? Here's a shortcut that displays all the formulas in the sheet at once:
Ctrl + ` (the acute accent key, found next to the number 1 on your keyboard). On a Mac, try Cmd + `
That's it! With the formulas displayed, you can click around to see which cells and functions are being referenced. You can toggle back to the values view by hitting the shortcut again.