A.2.11.2 Graphs of Two Equations

Here are two graphs that represent situations you have seen in earlier activities.  The first graph represents a = 450 - 20t, which describes the relationship between gallons of water in a tank and time in minutes.  a. Where on the graph can we see the 450? Where can we see the -20?  b. What do these numbers mean in this situation?

The second graph represents 6x + 9y = 75. It describes the relationship between pounds of almonds and figs and the dollar amount Clare spent on them.                Suppose a classmate says, “I am not sure the graph represents 6x + 9y = 75 because I don’t see the 6, 9, or 75 on the graph.” How would you show your classmate that the graph indeed represents this equation?