Can't prepare lesson material. Should I cancel class? I'm a grad student teaching assistant for a freshmen undergrad non major multivariable  calculus class.

What they didn't tell me is that the second half of the semester is not calculus but "finite math". This week's topic is game theory, which I've never learned myself.

In preparing tomorrow's material, I realized I was getting all the answers wrong from one of the sections, and have no idea how to do the problems I'm supposed to teach. Normally it only takes a day to read the textbook and prepare.

I've been up for hours struggling with the same problems and need to leave in 5 hours to get to class on time - and would still like to sleep.

My school never gave me any training or told me any rules; am I allowed to just cancel class?

I'll take any advice at this point.

Edit: I would just like to say how much I appreciate everyone's responses. I'm running on little sleep, (and extremely new to Stack Exchange so still learning how the site works) but you've all given me great ideas when I was truly stressing out.

Edit/Update: turns out I was not doing it incorrectly, just did algebraic work when I should've used a graph so I considered points that I didn't need to which is why my answers were wrong. I met up with the individual who TAd for the course last semester and that's how I figured out my mistake. I sorta winged it in presentation and got the correct answer, now just have to repeat the lesson for the rest of the sessions.

Thank you all for your input. 

Edit (from comment): Game theory is just one week of the course; they have two lectures with the professor prior to one 50 minute session with me. This is the only session with me out of a year long course that has been or will be like this.
I would like to add on top of the answers of @aparente001 and @Anonymous Mathematician.

So, first thing, in 5 hours it would be very hard to come up with something solid that you would be comfortable lecturing about; thus I second the suggestion of doing some review and exercises for now.

My opinion is: you can do it.

If you have been teaching calculus so far, chances are that you are a very competent student. You can learn almost at the same time as you will be teaching. And this does not have to be a stressful experience, I would say you can be upfront with your students and let them know that you are learning at the same time as them (they already know that you are a student too).

Actually, this can be beneficial for both parts: you) are learning a new topic and because of that you better understand the difficulties that students may come upon; they) have a TA that understands their difficulties and that is able to explain things in a way that a student would learn (it may not be the best way, but I would say that is OK).

In the case they make you questions you do not know how to answer, again, be upfront: say that it is a good question, you will think and research about it, and you will explain it later, either in the class, e-mail directly to the student, whatever you prefer.

In order for this to work, like mentioned in the other answers, you have to talk to your supervisor and let him know that you were not prepared to lecture this topic. Ask him for help about learning those concepts, or a reference to whom could provide such guidance.