<|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, 15, 39, 97], create an equation that equals 28. You can only use each number once and can use basic arithmetic operations (+, -, *, /). Show your work in <think> </think> tags. Also, return the final equation and result in <answer> </answer> tags, for example <answer> (num1 * num2) - num3 = result </answer>.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>