What are the names of expression and how do you break down a term?

What term best describes a line ans a point that lie in the same plane

Aschool puts on a play. the play costs $1,200 in expenses. the students charge $4.00 for tickets. there will be one performance of the play in an auditorium that seats 500 people. what is the domain of the function that shows the profit as a function of the number of tickets sold?  

Atriangle has a side lengths of 18cm, 80 cm and 81cm. classify it as acute obtuse or right?