Which is a description of an undefined term?

the distance along a line segment is the number of units between two points.

perpendicular lines are lines that intersect at a right angle.

a ray extends infinitely in one direction from an endpoint.

an angle is the figure formed by the intersection of two rays at a common endpoint

Which is a description of an undefined term?

The distance along a line segment is the number of units between two points.
Perpendicular lines are lines that intersect at a right angle.
A ray extends infinitely in one direction from an endpoint. 
An angle is the figure formed by the intersection of two rays at a common endpoint

The description of an undefined term is A ray extends infinitely in one direction from an endpoint. 

to find the perimeter, you add up all the lengths of the sides. in this case you would have to add up 18+22+40+80 which equals 160.