To simplify this expression, you combine the like terms, 6x and 4x. These are like terms because they have the same variable with the same exponents. Similarly, 8 and 2 are like terms because they are both constants, with no variables.
You are given the time and speed so from there you can get the points (2,50) and (6,54) once you got that you can see how the slope is 1 and b=48 x-y=-48 (standard form)