If two vectors combine in the same direction what mathematical operation would you use to find the resultant vector?

The head-to-tail rule is used to sum two vectors pointing in the same direction. (Vectors in the same direction are called collinear). The sum vector is slightly moved out of its correct position so that you can see it. For now, to determine if two vectors have the same direction look at a picture or use geometry.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.