What is the inverse of the statement “if an angle is a reflex angle, then it measures more than 180 degrees”?

Guests at an amusement park must be at least 54 inches tall to be able to ride the roller coaster. which graph represents the set of heights that satisfy this requirement?

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?

With alll of except for the 2 that i did already