What is the percent of change from 56 to 22? round to the nearest percent

Having a hard time understanding this question (see attachment).

Aremote-controlled boat can travel at 4 feet per second in calm water. the boat traveled 48 feet with the current, and then it traveled 16 feet against the current in the same amount of time. how fast is the current?

3/4 = c/36 i need with this fraction proble.