$9:4 visitors-$18:8 visitor is it proportional

An equation of the line tangent to y=x^3+3x^2+2 at its point of inflection is

How much dextrose 70% must be mixed with dextrose 5% to prepare 1,000 ml of dextrose 20%?

The first-serve percentage of a tennis player in a match is normally distributed with a standard deviation of 4.3%. if a sample of 15 random matches of the player is taken, the mean first-serve percentage is found to be 26.4%. what is the margin of error of the sample mean? a. 0.086% b. 0.533% c. 1.11% d. 2.22%