The ratio of the number of textbooks between A and B is 5:3. After A gives B 15 books, the number of textbooks is equal. How many textbooks do they share?
甲、乙两人课本数的比为5：3，甲给乙15本后，两人课本数相等，求两人共有课本多少本？
<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

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

<gadget id="calculator">(5/8) - (1/2)</gadget>
<output>1/8 = around 0.125</output>

<gadget id="calculator">15 / (1/8)</gadget>
<output>120</output>

<result>120</result>