The starting value is represented by the y intercept, which is the value y has when x=0. In the standard linear equation y=ax+b, the y intercept is b, so b=-4. The rate of change is the slope: at what rate does y change as x changes? So since a is the slope or rate of change the equation becomes y=7x-4, which is a rearrangement of y=-4+7x (Answer A).