Will bought a 144-ounce cooler filled with water

Describe in detail how you would construct a 95% confidence interval for a set of 30 data points whose mean is 20 and population standard deviation is 3. be sure to show that you know the formula and how to plug into it. also, clearly state the margin of error.

Someone me! if you’re smart you can solve this!

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9