Math homework help please?
1. The average of five weights is 13 grams. This set of five weights is then increased by another weight of 7 grams. What is the average weight of the six weights?
2.From a pile of 100 pennies(P), and 100 nickels(N), and 100 dimes(D), select 21 coins which have a total value of exactly $1.00. How many coins of each of the three types (P,N,D) should be selected?