Checking quiz answer

This isn't a Laravel project. I didn't feel Laravel was needed for it.

I created a small app that display slides to the user and after about 4 slides they are presented with a quiz to take. After completing the quiz they are then sent back to the slides to finish them up.

I'm having an issue on two items:

1. Hiding the navigation for the slides when the quiz is active.
2. Using a "Check Answer" button to see if the selected answer is correct and then displaying the correct response.

I am very new to Vue and I'm sure my code isn't as efficient as it could be.

https://jsfiddle.net/ThatWebGuy_/tg3khd7f/2/