How to find out how much you pay if there was a sale tax?

The surface area (sa) of a cube with a as the length of each of its sides is given by the formula . if the surface area is known, how can you rewrite the formula to find its side?

Mr.zimmerman invested $25,000 in an account that draws 1.4 interest, compouneded annually. what is the total value of the account after 15 years

Point r divides in the ratio 1 : 5. if the coordinates of e and f are (4, 8) and (11, 4), respectively, what are the coordinates of r to two decimal places?