How to do 4x + 5 equals 8

What is the equation of the graph that represents f(x)=x^4 stretched vertically by 2 and shifted up 3 spaces

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?

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15