What best describes a theorem in an axiomatic system

The multiplication property of zero states that the product of any number and 0 is 0. what must be true about either a or b to make ab=0

The measure of one angle of an octagon is two times smaller that of the other seven angles. what is the measure of each angle?

The monetary value earned for selling goods or services to customers is called a.) revenue b.) assets c.) money d.) accounting