The library teacher takes 1,000 yuan to buy two kinds of books A and B. If he buys 52 books of type A and 11 books of type B, the money will be used up; if he buys 40 books of type A and 20 books of type B, Just ran out of money. How much is each book of Type A?
图书馆老师带1000元去买甲、乙两种书，如果买52本甲种书、11本乙种书，正好把钱用完；如果买40本甲种书、20本乙种书，也正好把钱用完．每本甲种书多少元．
<gadget id="calculator">20 + 30</gadget>
<output>50</output>

<gadget id="calculator">1_000 / 50</gadget>
<output>20</output>

<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<gadget id="calculator">1_000 - 400</gadget>
<output>600</output>

<gadget id="calculator">600 / 40</gadget>
<output>15</output>

<result>15</result>