Question 1116909
<br>
let x = number of regular burgers
let y = number of double cheeseburgers
let z = number of regular cheeseburgers<br>
Then<br>
(1) x+y+z = 12  (the bun equation)
(2) x+2y+z = 15  (the patty equation)
(3) 2y+z = 11  (the cheese equation)<br>
There are many ways of solving systems of 3 equations; but for this one the equations are so similar that solving the system is simple.<br>
Comparing (1) and (2), we can see that y=3
Comparing (2) and (3), we can see that x=4
Then with x=4 and y=3, (1) tells us that z=5<br>
Answer: 4 regular; 3 double cheese; 5 regular cheese