Mary makes mugs.She makes 2 sizes of mugs:a small mug that she sells for $2.50 and a large mug that she sells for $5.75.Yesterday Mary made $56.Before she opened her shop in the morning,she had 200 mugs in her inventory.At the end of the day she had 188.How many mugs of each price did she sell?
12=x+y
56=2.50x+5.75y
continue on from there...