67.50 + 12.50 = 80
80/100 = 0,8 x 3 = 2.4
so, the total bill was 80 + 2.4 = 82.4
<em>hope it helps :)</em>
Standard error (SE)

Or

Therefore, SE of the mean = (8)/(2) =4
For the limit approaching 3 from the right, you want to follow the line to the right of x = 3. From the graph you're describing it sounds like that's y = -3.

The RHS limit is -3 even though f(3) = 7