In still water, the speed of ship A is 22 kilometers per hour, and the speed of ship B is 18 kilometers per hour. Ship B sails from a certain port and sails along the water. After 2 hours, ship A sails in the same direction. If the speed of the water flow is 1 hour 4 kilometers, how long can ship A catch up with ship B?
静水中，甲船速度是每小时22千米，乙船速度是每小时18千米，乙船先从某港开出顺水航行，2小时后甲船同方向开出，若水流速度为每小时4千米，求甲船几小时可以追上乙船？
<gadget id="calculator">18 + 4</gadget>
<output>22</output>

<gadget id="calculator">4 - 22</gadget>
<output>-18</output>

<gadget id="calculator">22 + (-18)</gadget>
<output>4</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">22 * (1/2)</gadget>
<output>11</output>

<result>11</result>