Question 8
Tien, Son and Dung each start with the same amount of money. At the bookstore, Tien buys 3 pencils and 4 notebooks and has 7 dollars left; Son buys 3 pencils and 3 notebooks and has 28 dollars left; Dung buys 1 pencil and 4 notebooks and has 21 dollars left. How much money did each friend have at first?
