Answer:
Air speed of bird is
mph
Explanation:
let the speed of the bird in still air be "X"
Speed of the bird when it flies in the direction of flow of wind 
Speed of the bird when it flies in the opposite direction of flow of wind 
The total time taken is equal to
minutes
hours
The distance in miles is equal to
miles

On solving the above equation, we get -

Air speed of bird is
mph
Radioactive dating can determine the age of minerals and fossils in each layer of rock.
Explanation:
Radioactive dating is the most commonly used geological method to determine the age of rocks and fossils layered in the layers of rock on the basis of their natural radioactive decaying.
With the help of the known rate of radioactive decay of isotopes, different types of radiometric dating are done depending upon the material found in the rock layers, like uranium-lead dating or potassium-argon dating.
Radiocarbon dating helps to record organic content in rocks like bones, shells, etc. Age of fossils sediment over sedimentary rocks is determined by combining with the bracketing method.