The probability of an event is 3/8. What is the probability the event will not happen

Answer choice:
3/8
5/8
37.5%
38%

The difference of 2 numbers is 21 and the quotient of the equation is 4 then what are the two numbers?

What is the gcf of 20c^3-5c^4+30c^6

If the angle bisectors of a pair of opposite angles of a quadrilateral are the opposite sides of a parallelogram formed by the two angle bisectors and two sides of the quadrilateral, is the quadrilateral always a parallelogram? explain your answer.