I am not getting forces at all. I 'm not sure of what to do. Here's the question: A box is resting on a flat surface. The box has a mass of 20KG and a force of 200N is pushing the box to the right. The force of friction acting on the box is 100 N to the left. What is the acceleration of the box? I know that the sum of the forces=Mass X Acceleration. But im not sure what numbers to put in.