B. ; everything means the same thing as the first.
Step-by-step explanation:
For a. we can tell what the expression means by re-reading the problem. We know that the 15 is the price per goby fish and that 10 is the price per shrimp. Since there is an equal number of each in each bag the x represent the number of goby fish or shrimp in the bag. The answer to the equation will be the price paid. Another expression you could use is the following.
This is an unfactored version of the first on where x is factored out. Here everything means the same thing it's just a different expression.