Let b be the price of the burger, c the price of the coke, and f the price of the french fries, then we can set the following system of equations:

Subtracting the second equation from the first one we get:

Now, subtracting the two times the above equation from the third equation we get:

Substituting c=2.75 in the third equation and solving for b we get:

Finally, substituting b=2.2 in the first equation and solving for f we get:

Answer: The burger costs $2.20, the price of the french fries is $3.15, and the price of the coke is $2.75.