<|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
In this challenge, your goal is to use the numbers [10, 21, 78, 92] and perform any combination of the following basic arithmetic operations (+, -, *, /) to come up with the target number of 81. Make sure to show your work in <think> </think> tags, and remember each number can only be used once. After your workings and showing the solution, return the final equation and your result in <answer> </answer> tags, for example <answer> (5 + 5) * 6 = 60 </answer>. Good luck!<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>