Michael pays $30 to enter a state fair plus $4 for each ride. Which of the following equations represent his total cost?

Michael pays a fixed $30, so lets put that by itself.

$30

Michael also has to pay $4 for each ride, so lets use a variable for that. I'll use r.

$4r

Now, since the problem said plus, we know to add.

$30 + $4r

That's your equation.