A has three times as many glass balls as B. If A gives B15 glass balls, then A has twice as many glass balls as B. Please do the math, how many glass balls A gives to B, the two have exactly the same number of glass balls.
A的玻璃球是B的3倍．若A给B15个玻璃球，这时A的玻璃球是B的2倍．请你算算，A给B多少个玻璃球，两人的玻璃球正好一样多．
<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">15 + 30</gadget>
<output>45</output>

<gadget id="calculator">3 - 2</gadget>
<output>1</output>

<gadget id="calculator">45 / 1</gadget>
<output>45</output>

<gadget id="calculator">45 * 3</gadget>
<output>135</output>

<gadget id="calculator">135 - 45</gadget>
<output>90</output>

<gadget id="calculator">90 / 2</gadget>
<output>45</output>

<result>45</result>