can someone explain how I can graph and plot ordered pairs with numbers like (1,75) (2,100) (3,125) (4,125) (5,150)

The ratio pv to nrt is plotted against pressure for ch4 at 0°c and 200°c. why does the curve for 0°c drop below the horizontal line for an ideal gas whereas the curve for 200°c does not?

What is a possible solutions of the x> 3?

Can someone me and do the problem plz so i can understand it more better