A flock of geese is attempting to fly due south, but the wind is blowing from the west at 5.1m/s. If the birds

can fly 7.5m/s relative to the air, what direction should they head?
(I'm assuming what direction should they head to fly due south....)

to fly due south, they need to fly "into the wind" such that their component of motion to the west exactly equals the wind speed to the east

if we call theta the angle between due south and their direction of travel, we need to choose theta such that

7.5 sin (theta) = 5.1

sin(theta) = 5.1/7.5

theta = 42.8 deg