Xiao Ming and Xiao Li went to the bookstore to buy books together. They bought 15 math books and 20 Chinese books in total. Among them, Xiao Ming’s math books were 4 times that of Xiao Li’s, and Xiao Li’s Chinese books were 3 times that of Xiao Ming. Then Xiao Li bought How many more books does Xiao Ming have?
小明和小莉一起去书店买书，共买了15本数学书和20本语文书，其中小明的数学书是小莉的4倍，而小莉的语文书是小明的3倍，那么小莉买的书比小明多多少本．
<gadget id="calculator">1 + 4</gadget>
<output>5</output>

<gadget id="calculator">15 / 5</gadget>
<output>3</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">20 - 5</gadget>
<output>15</output>

<gadget id="calculator">3 + 15</gadget>
<output>18</output>

<gadget id="calculator">15 - 3</gadget>
<output>12</output>

<gadget id="calculator">12 + 5</gadget>
<output>17</output>

<gadget id="calculator">18 - 17</gadget>
<output>1</output>

<result>1</result>