By joining all vertices of a decagon, how many diagonals are formed

Afactory adds 3 red drops and 2 blue drops of coloring to white paint to make each pint of purple paint. the factory will make 50 gallons of the purple paint. how many drops of red and blue coloring will the factory need in the 50 gallon batch of purple paint.

Amuffin recipe, which yields 12 muffins, calls for cup of milk for every 1 cups of flour. the same recipe calls for cup of coconut for every cup of chopped apple. to yield a batch of 30 muffins, how much flour will be needed in the mix?

Which one is the correct answer, and why?