<|im_start|>system
You are a helpful assistant. You first thinks about the reasoning process in the mind and then provides the user with the answer.<|im_end|>
<|im_start|>user
Challenge yourself to get to the number 81 using the numbers [1, 17, 20, 51]. Utilize the operations +, -, *, / with each number being used only once. Display your work within <think> </think> tags and provide the final answer as <answer> </answer>, for example: <answer> (1 * 17) * 20 - 51 = 81 </answer>. Remember to present three potential solutions in any order, one at a time. <|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>