ggreen eggs 2.25

regular eggs 2.00
ham 1.50
bacon 1.25
small drink 0.75
large drink 1.00
today's special 4.25

ticket #12;x+g+b=$5.50

what was ordered on ticket 12.

how do you know?
is there another possibility for the order? if so,, what is it?

g + b = 3.50

The order could have included

2 large drinks
or
1 regular eggs
or
bacon and 1 small drink