Can I write this
in CL? Or should I upload it as an image?
You would have to upload as an image to display like that.
You could do that, and explain that they may see something like:
Solve the following system of equations:
x+2y=14
3x-y=7
and that that means the same thing as the curly bracket.
Then perhaps explain that when they see that notation, they can use two separate expression boxes in Desmos to be able to graph the system.