Linear algebraic model

Question

Mark and Don are planning to sell each of their marble collections at a garage sale. If Don has 2 more than 5 times the number of marbles Mark has, how many does each boy have to sell if the total number of marbles is 128?

Answer 1

Let d and m be each boy's total.

d = 5m+2

d+m=128

Substituting for d:

5m+2 + m = 6m+2 = 128

6m = 126

m = 21

d = 5(21)+2 = 107