First of all, you're not stupid!!!!

Take Karen up on her offer of assistance, it might be just the thing you need.

It's just one quiz and you were doing fine before it.

Don't beat yourself up, know that you can/will do better next time.

I believe you can do it, if you believe it to you'll do so much better.

I'm not a math person either, in fact I quit math after grade 10, opting for accounting instead which was easier. Now I'm building spreadsheets for the entire company, because I can. I'm building spreadsheets for Engineers because they CAN'T. Have faith in yourself.