How to Figure Out the Difference in Cost of Something

There's a viral thing going around social media right now that gives a math equation and says, tell me how you do this in your head. Let's say it's something like, what is 46 or 46 plus 67? I would do the 40 and the 60 and the 6 and 7 and then put the two together. It was always really fun to see kind of the different ways that students figured out problems.