It is known that 900/((□-15)/15)=450, do you know how much □ is? (Write out the process of solving the problem)
已知900/((□-15)/15)=450，聪明的你知道□是多少吗？(写出解题过程)
<gadget id="calculator">900 / 450</gadget>
<output>2</output>

<gadget id="calculator">2 * 15</gadget>
<output>30</output>

<gadget id="calculator">30 + 15</gadget>
<output>45</output>

<result>45</result>