Solve the compound inequality and graph the solution

What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

You are at a restaurant and owe $38 for your meal. you want to leave a 20% tip. how much will your tip be?

Which describes the difference between the graph of f(x)=x^2 and g(x)=-(x^2-2)