A boat is headed due east (0) at 20 km/hr. A wind blowing to the south west at 18 km/hr is also acting upon it. What is the boat's velocity?

Vb = 20 - (18cos225 + i18sin225),

Vb = 20 - (-12.73 - i12.73),
Vb = 20 + 12.73 + i12.73,
Vb = 32.73 + i12.73,

Vb=sgrt((32.73)^2 + (12.73)^2)=35km/h.
= Velocity of the boat.