s: number of students
a: number of adults


Students paid 2 × s dollars and adults paid 3 × a dollars. They totaly paid $1050


2s + 3a = 1050

the sum of number of students and adults is given as 400


s + a = 400


Seems like a systems of linear equations question:


2s + 3a = 1050
s + a = 400


Multiply both sides of second equation with -2

2s + 3a = 1050
-2 × (s + a) = -2 × (400)


Add each sides of the equations:


2s + 3a = 1050
-2s - 2a = -800
------------------
a = 1050 -800 = 250 (number of adults)


Let's take the sum of the attendees equation:


s + a = 400


Let's plug the number of adults in the equation:


s + 250 = 400


(s + 250) -250 = (400) -250


s = 150 (number of students)


August 25, 2008, 7:33 pm

This website is totally informative.  Thank you for being here for individuals who need mathematic help.  Textbooks present these types of problems in the book, however they do not provide examples showing how to solve the problems.
May 30, 2009, 7:33 pm