I dunno, I would do a project with a social impact, maybe do something with carbon emissions. If you live near any university, then you can always get urself into a lab and work with them. That's a lot of fun and you get to do projects beyond ur school level.
Well its really not that hard,
I would set the two equations for the total number of tickets(y) based on the total number of employees (x)
y= 5x+15
y=7(x-5)
Based on that, you can find number of employees and then proceed to ur solution (the number of tickets). gl with SAT. xD.