(a) what is the equation of the line, written in slope-intercept form? show how you determined the equation.

First we need to find the slope.  We can find the slope by .  The slope is .  You can also find the slope by calculating the change in the y values over the change in the x values.  If the line looks like /, it has a positive slope, if it looks like \, it has a negative slope.  

The slope intercept form is

Where is slope and is the y-intercept.

To find the y-intercept is (0,16.25) because we take the last value we know, 15, and add (|m|).  So now we just put it all into the equation.