Aswimmer can swim in still water at a speed of 9.50 m/s. he intends to swim directly across the river that has a downstream current of 3.75 m/s. what is his velocity relative to the bank?

Refer to the diagram shown below.

Still-water speed  = 9.5 m/s
River speed = 3.75 m/s down stream.

The velocity of the swimmer relative to the bank is the vector sum of his still-water speed and the speed of the river.

The velocity relative to the bank is
V = √(9.5² + 3.75²) = 10.21 m/s

The downstream angle is
θ = tan⁻¹ 3.75/9.5 = 21.5°

  10.2 m/s at 21.5° downstream.