<|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
Utilize the numbers [15, 19, 43, 31], together with basic arithmetic operations (+, -, *, /), to form an equation that equals 73. Each number can be used only once. Display the final solution within <think> </think> tags. Then, return the completed equation and your solution in the expected answer format, as shown in the example: <answer> </answer>. For instance, one possible solution might look like <answer> (43 + 19) * 1.5 = 73 </answer>.<|im_end|>
<|im_start|>assistant
Let me solve this step by step.
<think>