Okay so, when you add four to a graph in this manner we have to look at the equation as a whole. f(x)=mx+b + 4. By adding four we are changing the y-intercept and shifting it up four. This will cause the entire graph to shift upwards four spaces.
Try a calculator and doing some googling of numbers divisible by six. There's a great calculator site called calculator soup! ( Yes it's really called calculator soup )
