First of all, let's find the slope, which is the rise/run. We have the points (-4,-3) and (-2,0). To get the run there, we move to the left two units. We rise up three units as well. Therefore our slope is positive. We have rise/run, which is 3/2 as our slope.
Now, b is the y-intercept, or when our line intersects with the y-axis. We can see that it intersects at a y-value of 3.
Every 2 inches is 5 miles right? we start off with 10 divided by 2, which gives us 2 inches, thats one step done! now we need to do .6 divided by two, .5 is 1 and .1 is .2. our answer should be 3.2 inches.