In this video the instructor shows how to do temperature conversions using y = m*x + b. Now if Celsius is represented by the variable C and Fahrenheit is represented by the symbol F, you can replace then in the previous equation in place of the variables x and y giving you the equation C = m*F + b. Now to solve for the values of the constants m and b you need to have values of two sample temperatures in both Celsius and Fahrenheit. Take the first sample and substitute in the above equation giving you a liner equation with two unknowns. Similarly substitute the second sample to obtain the other equation. Solve these two equations there by obtaining the values of m and b. Finally substitute these values in the C = m*F + b equation and you will get the general formula to convert temperatures. This video shows how to convert temperatures by deriving a general formula.