Add them all up.
A triangle has 3 sides, and you said each side is 3. So:
3+3+3 = 9
The rent for one book for one week is thirteen dollars and thirty-three cents.
Is e just an algebraic expression or is it Euler's number (2.718...)?
If e is an algebraic expression then there it is
The error to that problem is the person switched the x and y points, like in point A, it’s supposed to be (x,y) or (1,5). The person put the y in front of the x while writing the points.