1.what if they changed the scoring system in American Football, and there were only two ways o score, a field goal worth 3 points and a touchdown worth 7 points. What are all the possible total scores that a team could have?

Answer 1

all multiples of 3 and 7, added together:

3,6,9,12,...
7,14,21,28,...
and sums of those rows in all combinations.