Total time = upstream time + downstream time he rowed the same distance both ways. upstream time = D/4 downstream time = D/6 total time = D/4 + D/6 = 3D/12 + 2D/12 = 5D/12 = 3 hours D = 3*12/5 = 36/5 or 7.2 miles where D is the one-way distance. The total distance he rowed is 2*D = 72/5 or 14.4 miles