PLEASE PROVIDE FULL EXPLANATION WITH EACH SOLUTIONS. DON'T UNDERESTIMATE THESE QUESTIONS.

1.An artist has red and blue paint. To make a shade of purple, they will combine the red and blue paints. They will combine no more than 10 parts of paint. Combinations that have the same ratio of colors will produce the same shade of paint. For example, one part of red and one part of blue will result in the same shade as two parts of red and two parts of blue. If they can not combine fractional "parts" of paint (For example, they can't use 1 parts blue), how many different shades of paint can they make?

2.In my change bowl, I have exactly $1.80 worth of pennies, nickels, dimes and quarters. I have no more than ten of each coin. How many different combinations of coins could I have?

3.I have a collection of exactly 20 coins that total exactly $2.00. How many combinations of coin can I have?