Let B = number of burgers
B - 2 = number of fries
D = number of drinks.
B + (B - 2) + D = 53
B + B - 2 + D = 53
2B + D = 55
6·B + 3·(B - 2) + 2·D = 204.00
6B + 3B - 6 + 2D = 204.00
9b + 2D = 210.00
Combining these two equations:
9B + 2D = 210 ---> 9B + 2D = 210
2B + D = 55 ---> (multiply by -2) ---> -4B - 2D = -110
(adding down the columns) 5B = 100
B = 20
Since 2B + D = 55 ---> 2(20) + D = 55 ---> D = 15
Since the number of burgers is 20, the number of fries is 18, and the number of drinks is 15.