So, the bag weights 11

, that is 11.5,, and also that is

correct?
I changed it into an improper fraction, because the division will be easier later.
A serving is

. So what we need to do is the divide the weight of the bag, that is

by the weight of the serving, that is

.
a division by fraction is a multiplication by its inverse, like this:

*

now we can simplify: the denominator of the first and the nominator of second are multilications of 2:

*

so there are 15 servings and a little will be left over.