The Display command uses the Typesetting package native to Maple Document mode. However since Möbius is a web app, everything needs to be converted into MathML (or LaTeX or similar) to be supported by the browsers.
The closest I can think of (with this method) is the following: $a=maple("use InertForm:-NoSimpl in a:=2(3*x) end use; printf(InertForm:-ToMathML(a));");
But I don't know if that will generalize well to the rest of your problem.
One solution to this would be to hold the answer in a variable. For example to calculate power = energy/time we could use variables such that $P = $E/$T. In the response area (assuming you are using numeric) you can then set "Required with" to "absolute accuracy". If you are using randomisation such that $P would be to more than two significant figures you can use the command "decimal(n,x)" in the algorithm section where x is the input and n is the number of decimal places. In this case it would be decimal(2,$P).
It seems that they have an iframe embedder feature, so it's pretty much copy-paste of their source code into source code of a Mobius question. I've attached a TA question with one of their demos as an example: Example.zip
If you're comfortable with Maple programming language, you can try 'inert form'. It will allow you to grade student response in its original form, without simplifications. Click here for an example.
Alternatively, you can convert the response to "string" and use string tools to check if the expression contains (the right number of) brackets, this should allow you to identify the expression type. I'm thinking alongs the lines of: student answer is equal to the correct answer AND the number of "(" brackets is right.
With regards to "y=" part. It's hard to say without the actual grading code. You could try to pull the the equation apart with use of lhs and rhs commands. For example, "y= a + b" would give you "y" and "a+b" respectively. This should allow you to grade equation in two parts without equation comparisons.
When assigning variable names to the equations (Maple syntax) I often forget to use ":", for example: "my_equation = y = a+b" instead of "my_equation := y = a+b". This leads to similar error messages.
The 40px spacing applies to the iframe for the entire HTML question. Whilst your trick worked for me, I'd suggest moving all of your Question Text to inside the Question HTML: part of the response area:
I have been able to search for content in the Cloud in Maple T.A. 2017 - e.g. searching for Distribution gives any folder with 'Distribution' in the title, as well as questions containing 'Distribution' in either the title or the question text. Can also use * to search the start of words e.g. searching Geom* will give you results for Geometry and Geometric. However I'm afraid I don't see the Fourier series folders you are referring to (either in the list or by searching).
EDIT: Also if you are looking for a specific topic, try the "Subjects" list under Maple Cloud, instead of "All Content Types".
@chrisb@mcla Thank you both for the math app files, these look good! Preferably I would want the option to draw both linear lines and hyperboles, so if you know of a way to do this let me know. For now, I will try to adjust these math apps a bit to fit my needs, but I am not that skilled yet at Mathapp, so if you have any tips, please let me know