So you have to make two equations. Let's say x stands for shirts and y stands for pants. 4x+3y=85.50. The second equation would be, 5y=115-3x. Since you need one of them to have x= or y=, you need to change it to that form. y=. Then you do substitution and solve which leaves you with:
Shirts are $7.50
Pants are $18.50