Teacher Wang bought a house by installments. There are two payment methods: 20,000 yuan in the first year and 10,000 yuan a year thereafter; 7500 yuan. The payment amount and timing are the same for both payment methods. May I ask how much is the price of this house Mr. Wang bought?
王老师以分期付款的方式购买了一套住房，买时有两种付款方式：第一年付20000元，以后每一年付10000元；或者前一半时间每年付15000元，后一半时间每年付7500元．两种付款方式的付款总额和时间都相同．请问王老师购买的这套住房的价格是多少元？
<gadget id="calculator">20_000 - 10_000</gadget>
<output>10_000</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">15_000 * (1/2)</gadget>
<output>7_500</output>

<gadget id="calculator">7_500 * (1/2)</gadget>
<output>3_750</output>

<gadget id="calculator">3_750 - 10_000</gadget>
<output>-6_250</output>

<gadget id="calculator">7_500 + (-6_250)</gadget>
<output>1_250</output>

<gadget id="calculator">10_000 / 1_250</gadget>
<output>8</output>

<gadget id="calculator">8 - 1</gadget>
<output>7</output>

<gadget id="calculator">7 * 10_000</gadget>
<output>70_000</output>

<gadget id="calculator">20_000 + 70_000</gadget>
<output>90_000</output>

<result>90_000</result>