The base of a triangle is 5 cm. If the length of the base increases by 1 cm, the area of the triangle increases by 3 cm2. What is the area of the original triangle in square centimeters?
一个三角形底为5厘米，如果底边长增加1厘米，这个三角形的面积增加3平方厘米．原三角形的面积是多少平方厘米．
<gadget id="calculator">2 / 1</gadget>
<output>2</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">6 / 2</gadget>
<output>3</output>

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

<result>15</result>