You've been posting long enough to know that you must do your work before anyone can help you. So what are your thoughts on the matter? Are the enthalpy and entropy of reactants and products constant? If they change with temperature, is the rate of change the same for all reactants and products?
It is a simplification in early undergrad chemistry. When you get to real thermodynamics, you will see that this is not true, they will give you the tools then that will aid you.
Although in some cases the change in enthalphy is so small according to temperature that you can use a weighted value.