In these types of problems, you will get two equations: the first equation relates to the dollars and the second equation relates to "how many".

OK, lets call advance tickets = a and door tickets = d. These are our unknowns.

The first equation is about the money. $7a+$9d=$5740.

The second equation is about how many. a+d=684.

We have 2 equations and 2 unknowns, so we can use substitution method to solve this thing! Let's rewrite the second equation a=684-d (you could also solve this by writing d=684-a, you choose).

Substituting our new second equation into our first equation, we get

$7(684-d)+$9d=$5740. Now using your skills to solve equations, here are the steps:

4788-7d+9d=5740

4788+2d=5740

2d=952

Cornelia M.

Sorry, WyzAnt just cut me off mid-solve!!

I was at 2d=952

d=476.

Therefore, 476 tickets were sold at the door.

09/24/12