Use proportions:

Solve for d.

Use the definition ofb) If Earth makes one revolution every 24 hours, what is the linear velocity of a point near the equator?

Having severe trouble over here. For a) I know the difference of their latitudes is 6degrees20minutes but I don't know what to do from there.

And for b) I did (4000)(2pi/24). I don't know if it's right though.

The result is in