How do you know if lines are parallel?

1. if events a and b are non-overlapping events, how do you find the probability that one or the other occurs? 2. what does it mean if p(a or b) equals 1?

Larry wants to buy some carpeting for his living room. the length of the room is 4 times the width and the total area of the room is 16 square meters. what is the length of the living room

In the diagram, ab is tangent to c, ab = 4 inches, and ad = 2 inches. find the radius of the circle.