There is a wall with a length of 6 meters and a height of 3 meters. In the middle is a window with a width of 5 meters and a height of 1 meter. What is the area of this wall?
有一面长6米高3米的墙壁，中间是宽5米，高1米的窗户，这面墙的面积是多少？
<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">5 * 1</gadget>
<output>5</output>

<gadget id="calculator">18 - 5</gadget>
<output>13</output>

<result>13</result>