



 
Hi Ann, I can prove that your answer is correct as follows.
I don't however think that this is what the teacher wants. The teacher wants to know how you arrived at the answer of 3 lbs. I expect that the teacher is looking for something like this.
Continue by expressing the weight of the first fish in terms of $x.$ Add the three weights and set the result equal to 21 lbs. Solve this equation for $x.$ Penny  


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