On a coordinate diagram the horizontal line is called the
xaxis and the vertical line is called the
yaxis. The point where the xaxis and yaxis meet is called the
origin, O.
The coordinates of a point are written (a,b) where a is the distance across (left or right) and b is the distance up or down from the point (0,0).
Plot the point A(3,4) on a rectangular coordinate system.
The point A(3,4) is three units to the right of the vertical axis and 4 units above the horizontal axis.
Finding coordinates of Points
Look at the reverse problem that is, you are given points on a rectangular coordinate system and are asked to determine their coordinates.
Determine the coordinates of each of the points
Point 

Position 

Coordinates 
A 

Two units right, two units up 

(2,2) 
B 

Two units left, one unit up 

(2,1) 
C 

One unit right, three units down 

(1,3) 