Why cant the exponents be added in the product 14^5 • 18^3?

The last time i bought this product , it cost $20.00 but it looks like it cost 29. 60 today? what is the increase

To make a monster appear large in a movie, a human actor wore a costume and walked through a scale model of a city. the scale used was 1 inch = 15 feet. the actor is 60 inches tall. how tall does the monster appear in the movie? question 5 options: 720 feet 75 feet 4 feet 900 feet

If you answer right ill give brainliest, : )