Nina takes her friends to an ice cream store. A milkshake costs $3 and a chocolate sundae costs $2.50. Nina has $18 in her purse.
Let m = milkshake
Let c = chocolate sundae
a) Write an inequality to describe how Nina can spend her money.
b) What are 3 combinations of milkshakes and chocolate sundaes that Nina can spend and still have change from $18?