The question on the top old explain

So it's asking you to create an expression on how much you spent.
So you have already spent $30 on a DVD and $20 for a CD. And we don't know how much the videos are so that is x.
Your equation is going to be something like 30+20+5x but since it says it wants it in simplest form it's going to be 50+5x or 5x+50 either way that will be your equation answer. The reason it's that equation is because we know how much you spent already which is 50 and since you bought 5 videos of an unknown number that's how you get 5x.
50+5x

Divide 40%5 and your answer is 8