Final answer:
Without the original problem and Nicholas's solution, we cannot determine his specific mistake. However, common problems can be resolved using various mathematical problem-solving strategies.
Step-by-step explanation:
The question provided does not give enough specific information to identify Nicholas' mistake in the homework problem he discussed with Alma. To determine what his mistake was, we would need the original problem, Nicholas's full solution, and preferably the feedback that indicates where he went wrong. Common mathematical mistakes can include calculation errors, misunderstanding the problem, applying the wrong formulas or concepts, or making errors in algebraic manipulation. These issues can be addressed through problem-solving strategies like identifying knowns and unknowns, ensuring all steps are followed correctly, and checking if the answer is reasonable.