<|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
Using the numbers [3, 8, 45, 21], make an equation that equals 72. Each number can be used only once. Demonstrate your work in <think> </think> tags. And return the final equation in <answer> </answer> tags, similar to the above format.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>