Can anybody help me with my geo hw problem

Statement: if two points are given, then exactly one line can be drawn through those two points. which geometry term does the statement represent? defined term postulate theorem undefined term

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)

Aclassroom is made up of 11 boys and 14 girls. the teacher has four main classroom responsibilities that she wants to hand out to four different students (one for each of the four students). if the teacher chooses 4 of the students at random, then what is the probability that the four students chosen to complete the responsibilities will be all boys?