<|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 [15, 17, 21, 25], create an equation that equals 30. You can use basic arithmetic operations (+, -, *, /) and each number can only be used once. Note that these numbers are close but non-trivial and require a bit of thinking. Here are some potential equations you may consider: 15 + 15 = 30, or 25 - 21 = 4, then multiply by 17 to get 30. Please show your work in <think> </think> tags. And return the final equation and answer in <answer> </answer> tags, for example <answer> (15 + 15) / 3 = 10 </answer>.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>