Trying to build an online web based exam for my students and stuck on how to build the questions so that students can show working

Due to covid, I am trying to build an online assessment/exam for my students. This is basically math assignments. I haven't started coding, and still in the planning stage.

The problem I have is that it is an important requirement that the students can show their working. The answers will be multiple choice so marking it can be automated. However I am looking to see that the students have shown working, or at the very least, have the opportunity to do working without having to print screenshots or transcribe the question onto paper.

So take a trivial question such as:

37+
23
--  

I would like for example in this case that the student could show how they carry 1 and put a 60 under the line.

They can choose from

a) 50
b) 60
c) 70
d) 80

I was thinking of making the question an image like a .GIF and then using it as a background image, and then trying to find some type of web control that allows them to type anywhere to show their working. It might also be the case that they could draw lines and shapes as part of it.

Any suggestions on:

1. Approach to take
2. Language to use
3. Any specific controls, libraries to use to allow for this.

Thanks!