The depth of the river is 4m. A bird flies to 10m above the river. How many meters is the image of the bird in the river from the river?
河水的深度为4m，有一只鸟飞到河面上空10m处，此时鸟在河中的像距河面是多少米？
<gadget id="calculator">10 + 10</gadget>
<output>20</output>

<result>20</result>