You will need to type your problem sets and submit them as PDF files. The path of least resistance is to use Markdown to do so (however you can use other methods such as LaTeX if it is more convenient). This is a lightly annotated form of plain text which we use to write the problem sets as well. We will provide the markdown sources for each problem set, and so it should be very easy for you to edit your homeworks.
The least overhead solution is to use an online markdown editor such as hackmd, classeur, stackedit, or madoko. Just make sure you are able to export to PDF, since in some of these services PDF export is a “premium feature”. You can also often use the “print dialog” of your browser to print to pdf. The final look of the PDF does not matter so much, as long as the text and ordering matches the problem set.
Of course, using online editors has its drawbacks with relying on Internet connectivity etc…
And so a more robust approach is to install
a program such as pandoc (available for Windows, Mac and Linux) which allows you to compile markdown files (which can be edited in any text editor) into PDF.
To produce PDF files using pandoc you will also need a TeX installation such as MikTex for Windows, TexLive for Windows/Linux, or MacTex for Macs.
All the problem sets in this course are written in markdown and compiled to PDF via pandoc.
Specifically the command used is pandoc --pdf-engine=xelatex --variable urlcolor=cyan -o homeworkx.pdf homeworkx.md (replacing x with the homework number).
Markdown files are simply plaintext files (traditionally with an .md extension), and can be edited using any text editor.
I personally use Atom which has the Markdown Preview Plus package that can be helpful (you can also try markdown-preview-enhanced).
To write math using markdown (or, more accurately, using certain markdown flavors, such as those of pandoc and stackedit), you write Tex/LaTeX math between $ signs as in $e^{i \pi}= -1$ or $$\sum_{i=0}^n (i+1)^2 = n(n+1)/2$$ to generate in-line or displayed equations respectively.
(Some markdown editors, such as Dillinger require double dollar signs.)
Some trial and error is probably the best way to learn TeX/LaTeX math, but one good starting point is this section in the LaTeX wikibook.
Here is one useful list of LaTex symbols (see also this cheat sheet ) and you can also use the DeTexify website to draw a symbol and get the corresponding LaTeX code.