The store ships back 150 phones, sells 55 in the first week, sells 20 more in the second week than the first, how many are left unsold?
商店运回150部手机，第一周卖出55部，第二周卖出的比第一周多20部，还有多少部没卖出？
<gadget id="calculator">55 + 20</gadget>
<output>75</output>

<gadget id="calculator">150 - 55 - 75</gadget>
<output>20</output>

<result>20</result>