At a concert, a band sold t-shirts for $18 and hats for $12. They sold 60 t-shirts and hats combined for a total of $870. How many t-shirts did they sell? How many hats?
Let x be the number of t-shirts sold. Let 60-x be the number of hats sold. They have a total cost of 870. We form an equation:
25 t-shirts were sold and 60-25=35 hats.