A girl is at point A on a bank of a straight river which is two miles wide. She wants to reach point B, which is across the river and 7 miles downstream, by first rowing her boat to a point P on the opposite bank and then walking the remaining distance, x, to B. She can row at 4 miles/hour and walk at 3 miles/hour. Express the total time T that she takes to go from A to B as a function of x.
HINT:
Draw a perpendicular from P across the river to a point M. Calculate the hypotenuse of triangle APM to find distance rowed as a function of x. x is distance walked. Remember that these are distances, so to get time one must divide by the rate. Note that leg AM is 7 - x.