Your brother bikes 350 miles in 27 seconds how fast did he go

His speed is exactly (350/27) miles per second ... about 46,667 mph. Wotta guy !

The answer is as follows in the photo

The boat's velocity relative to the riverbank can be resolved into two components. the component going north is 2.7 m/s and the component going west is 1.2 m/s.we add these two vectors and then find the magnitude of the resultant to get the speed.the magnitude of the resultant vector from adding can be obtained by the pythagorean theorem.    to two significant figures, the boat's speed relative to the riverbank is 3.0 m/s.