The cost for the 3 goldfish would be 3*1.90 = 5.70 The cost for the 3 angelfish would be 3*6.10 = 18.30 The cost for the 12 neon tetras would be 12*1.53 = 18.36 So the total cost would be given by the following equation: 3*1.90 + 3*6.10 + 12*1.53 =5...