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Select all the correct answers. what is 221,000,000,000,000,000,000 expressed in scientific notation?

Astandard american eskimo dog has a mean weight of 30 pounds with a standard deviation of 2 pounds. assuming the weights of standard eskimo dogs are normally distributed, what range of weights would 99.7% of the dogs have? approximately 26–34 pounds approximately 24–36 pounds approximately 28–32 pounds approximately 29–31 pounds

What is the result of adding the system of equations? 2x+y=4 3x-y=6