How can you determine that a coin is not pure silver if you know the mass and volume of the coin

What two advantages do the coastal countries of west africa have over the sahel countriesfertile soil and mineral resources temperatures and terrain human resources and natural resources weather patterns and location

What is an additional type of erosion found at the coast? what does it mean?

Name the two rivers that run through the fertile crescent. how were the rivers both positive and negative to societies of the fertile crescent?