When you have finished this page, try the Equations 6 Quiz.
RECAP: In the previous pages,we learned about equations with positive and negative numbers. On this page, we will learn about two different mystery doors.
Is it possible to have more than one mystery door? Actually, one could have many mystery doors. However, it makes it possible for there to also be many different answers to the same equation. Let's take a look at an equation. Black door plus red door equal five.

+ 

= 
3 
In one case the number 3 could be behind one door and the number 0 behind the other. In another the number 2 could be behind one door and 1 behind the other. There could be decimal numbers as well as positive and negative numbers. Can you think of other combinations?
To adequately show the infinite possibilities in such an equation, one can use a graph that shows the two different answers as coordinates. Look at the graph below. Notice the line that is drawn across the grid. The line crosses points such as (0,3), (1,2), (2,1), (3,0). If more of the grid were drawn and the line was extended, one would cross such coordinates as (4, 1), (1, 4), (5, 2), (2, 5), etc..
x + y = 3 
