The secret of doing this math question, it is important to understand what we have first and use the power of consecutive information from the Q1 to Q3. And think about when we Stacked woods to build up something like a house, we need to put one block and follows by another block after that, and we get what we want finally. Or something like playing dominoes, you can get the final result after one block after another block. Otherwise, you skip one of the block, it is impossible to get an amazing result, just like this math problem. We need to focus on the continuity of everything we have already known. Think about what we have from the questions of one and two. And keep the continuity to figure out the solution of question 3. By this way, answers will appear immediately.