Rise=16, run=7. Slope is rise/run, and therefore is 16/7. The run is considered to be the x coordinate. Since the x coordinate on the point is 21, we know it has moved 3 exact points away from the origin (21/7=3). We can use this movement of 3 exact points to determine the y coordinate as well. Since the rise (y) is 16 for every exact point on a graph, we know the graph has risen 48 units (16x3=48). So, the point ends up being (21,48). The rate of change is 16cm per 7 minutes, or 2.28cm/minute. The equation is Y=(16/7)X (no y intercept because the graph starts at the origin). The equation gives you the y value of 48 when x is equal to 21.
How? When they say directly you should multiply the x and y together. You would get -24, now using that number divide -24 by the new x(-6) you would get 4.
