Doppler Effect QUestion?

Question

On the planet, a man is flying toward his mate at 25 m/s while singing at a frequency of 1200Hz. If the stationary female hears a tone of 1240Hz, what is the speed of sound in the atmosphere?

Answer 1

f_observed = f_emitted ( v / ( v - vs ) )

where f_observed is 1240, f_emitted is 1200, and vs is 25 m/s. Solve for v, the speed of sound.