Lets see if I can explain this.
The x axis, or first number used is the bottom line, from 0 to 10.
The y axis, or second number used is the side line, from 0 to 100.
Your point should be (2,20) not (20,2) as you always go left or right before up or down. That means that your slope = the change in y divided by the change in x or 20/2. That equals 10.
The slope represents that number of gallons of gas needed to drive a certain distance. For every 1 gallon of gas you use, you drive 10 miles, or for the points you have marked on your paper, for every 2 gallons of gas you use, you drive 20 miles.
Always use the left to right numbers first, before the up and down number on the side.
#1 = the slope is 10.
#2 = The slope represents that number of gallons of gas needed to drive a certain distance. In this case, for every 2 gallons of gas, you drive 20 miles.