What would the equation be for: six times the sum of one-half and a number equals twenty-one times a number

Using d, e, and f as values on a triangle and d being 60 degrees, what is the value of e and f if d is 60 degrees? also, what do you notice about the values of e and f?

Calculate the missing value. round the answer to on decimal place. start with 70, increase it by 21%, and end up with

What is the area of a rectangle with vertices (-8,-2), (-3,-2), (-3,-6), and (-8,-6)? units