Mark and Don are planning to sell each of their marble collections at a garage sale. If Don has 7 more than 2 times the number of marbles Mark has, how many does each boy have to sell if the total number of marbles is 67?

This is what i found “an explicit formula designates the nth term of the sequence, as an expression of n (where n = the term's location). it defines the sequence as a formula in terms of n. this example is an arithmetic sequence(the same number, 5, is added to each term to get to the next term).” i hope this you for what your looking for. can you plz mark me brainliest?