Given data:
The calories in milkshake compare to double cheeseburger is x=2y+720.
The total calories in two double cheeseburger and chocolate shake is x+2y=2040.
Here, x is the number of calories in milkshakke and y is the number of calories in cheeseburger.
Substitute value of x in the second equation.
(2y+720)+2y=2040
4y=2040-720
y=330
The value of x is
x=2(330)+720
=1380
Thus, the number of calories in milkshake is 1380 and in the double cheese burger is 330.