Which graph represents a function?

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.

You paid 28.00 for 8 gallons of gasoline. how much would you pay for 15 gallons of gasoline?

In the polynomial below, what number should replace the question mark to produce a difference of squares? x2 + ? x - 36