A wave raises a buoy twice every second and the crests of the incoming waves are 4m apart what is the wavelength in meters?

You just said that the crests of the incoming waves are 4m apart.

That's it ! That's the wavelength. The distance between crests. It doesn't matter how often they sail past you.

The question I was expecting here: How fast are the waves traveling ?

That's (frequency)x(wavelength). 8 m/s.

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.