The pier of a bridge is 18.25 meters high, of which 4.27 meters are underground and 6.09 meters are above the water. How deep is the river in meters?
一座桥的桥墩高18.25米，其中4.27米在地下，6.09米高出水面．河水深多少米？
<gadget id="calculator">18.25 - 4.27 - 6.09</gadget>
<output>7.89</output>

<result>7.89</result>