4x+8= x because, you already know that the last fish he caught weighed 8 pounds so you do not have to do anything to that number and you know he caught 4 fish so if all four fish weighed the same you would just multiply 4(the number of fish) and x which represents the weight of the fish. So 4 times x equals the total weight of the four fish plus the 8 pounds of the last fish should get you the total weight of all the fish he caught.