A rectangle is 12 cm long and 5 cm wide. If the length and width are increased by 3 centimeters, by how many square centimeters does the area of the rectangle increase?
一个长方形长12厘米、宽5厘米．将长和宽分别增加3厘米，那么这个长方形的面积增加多少平方厘米？
<gadget id="calculator">12 + 3</gadget>
<output>15</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<gadget id="calculator">15 * 8</gadget>
<output>120</output>

<gadget id="calculator">12 * 5</gadget>
<output>60</output>

<gadget id="calculator">120 - 60</gadget>
<output>60</output>

<result>60</result>