Relations between 2 quantities

In this example we can see that the X value (also known as input or independent variable) is 1,2,3 and that the Y value (also known as the output or dependent variable) is 18,21,24 and on a grid these pairs called ordered pairs would be points on the graph and for these we put the X value first and the Y value second which gives us an ordered pair which is a graph point so in this situation we would have 3 ordered pairs (1,18),(2,21) and (3,24).