Eric buys a coffee table price d at $100. If the sales taxis 5%, what wil lbe the total cost including tax?

The concept that can be used in order to measure the given item is the ratio and proportion. The ratio of Nicole's height to her shadow at that particular time should be equal to the ratio of the height of the tower to its shadow. If we let x be the height of the tower then, the equation would be,

       x/20 feet = 5 ft/80 inches

The units of the denominators should be equal to have a reasonable comparison, let us convert 80 inches to feet by dividing it by 12 to get the answer of 20/3 ft. 

           x/20 = 5/(20/3)

The value of x from the equation is equal to 15 ft. 

15 ft.