Me with math.. im dying/drying/frying

what is the difference between a ray and a plane?

A ray is a line that has a begining point, but no end point
 a ray is 1 dimentional, it only goes one direction, left and right

a plane is 2 dimentional and extends indefinitely
it goes left and right and up and down

think of it like this

you have a piece of paper with no height
you draw a line starting at a point on the paper and it goes infinitely in the other direction

the paper is a plane, the line on it that has a starting point is the ray

Divide 40%5 and your answer is 8