Linear functions always go up by the same value. You can subtract 2 y values and divide it by the corresponding x values (subtracted the same way) and you will get the same number. Here is an example from ur chart. 3). (9-7)/(3-2) = 2. Now try it for another two values. You get 2. That means it is linear. The equation for it would be y=2x+3
Now do the next one good luck!
