Its a because it should be 50 50 if u think whats 100/2 so that would be a simple event
It is used to see if a graph represents a function because if there is 2 dots or intersecting lines within the other lines then it is not a function. if there is only one line or dot, then yes, it is a function. hope i explained it well.
Look at the pictures (examples)
m∠1 = m∠6 → answer: none
m∠2 = m∠3 → answer: none
m∠2 = m∠C → answer: none