Here is the answer to the given problem above. Let x be the number of parents and y for the children. x + 3y = 40 2x + 3y = 53 x = 40 - 3y 2(40-3y) + 3y = 53 80 -6y + 3y = 53 80 - 3y = 53 -3y = 53 - 80 -3y = -27 (divide both sides by -3) y = 9 This means that the cost per child is $9 Now solve for x x = 40 - 3y x = 40 - 3 (9) x = 40 - 27 x = 13 So the cost per parent is $13. Hope this answers your question.