When starting to type this comment, I was going to write that I could not do it and I think of myself as a decent coder. While typing that, I had an idea and I started a stopwatch...
Made this test set in the first minute: "1 + 1", "1 * 2", "1 + 2 * 2", "1-1", "1/2", "1+2/2" which I think should cover the requirements generally. Then I took 9m58s to come up with 77 super ugly lines that, to my surprise, after fixing that I forgot to cast the inputs to floating points (lines 67 and 76), gave the right answer straight away.
Code and output: https://pastebin.com/C3RVqpjE
The correct answer would probably have imported ast but, while I know of the general existence of such tools, I never needed this in my life. It's not like I work on JSON parsers (a minefield) or wrote my own coding language. An old colleague did the latter for a commercial product by using str.split on operators (yes, strings were a major feature in the language), which went about as well as you expect... I know to stay away from these problems or, if tasked with it, where to look to solve it, but that doesn't mean I can do it in an interview.
While I'm pleasantly surprised to have gotten a crude version working and in a faster time than I expected...
...if you're not hiring specifically for a parsing job, please don't use this as a coding exercise. It could be an interview question if you just want to hear "something something AST, and not by string-splitting on operators when the language has strings with said operators potentially in them". That could demonstrate knowledge sufficient such that the coder would do the right thing if this task were to come up in their job