One day, a deli sold a total of 37 hamburgers and hot dogs. The revenue from these sales was $147.88. The hamburgers were $5.29 each and the hot dogs cost $2.10 each.
a) Write a mathematical expression for the number of burgers, x, and the number of hot dogs, y, sold that day.
b) Write a mathematical expression for the amount of revenue from this day's sales. Use x for the number of burgers and y for the number of hot dogs.
c) How many burgers did the store sell that day? (Include the word burgers in your answer).