The 18 good friends in the graduation class took a group photo. If you take a 6-inch photo, you can get 3 photos directly. The price is 6.6 yuan. How much does a person have to pay.
毕业班的18名好朋友合影，照6寸照片可直接得3张照片，价格是6.6元，另外加洗，使每人各得一张照片，加洗一张的价格是1元，平均每人要付多少元．
<gadget id="calculator">18 - 3</gadget>
<output>15</output>

<gadget id="calculator">1 * 15</gadget>
<output>15</output>

<gadget id="calculator">6.6 + 15</gadget>
<output>21.6</output>

<gadget id="calculator">21.6 / 18</gadget>
<output>1.2</output>

<result>1.2</result>