Newton's second law of motion describes the relationship between force and acceleration. They are directly proportional. If you increase the force applied to an object, the acceleration of that object increases by the same factor. In short, force equals mass times acceleration.
Distributive Property means you multiply each component by the value you are distributing in this case: (1/2)(10x) + (1/2)(20y) + (1/2)(10z) which will yield 5x+10y+5z