Then use the homework to review for exams. You learn little or nothing by doing this. After numbers are substituted and manipulated, you lose track of the identity of things. This makes it difficult to discover where you might have went wrong. The magic point is learned by experience.
Numbers alone are half the problem and are senseless unless the units are also specified.
If at the end of a problem, you are trying to do something like this, you did something wrong. You learn when you do it yourself. He is also your most underused and undervalued resource. The ultimate test of learning is the ability to apply principles or relationships to problems you have not seen before. Your exams may be so constructed.