Nick starts with 20 milligrams of a radioactive substance. The amount of the substance decreases by 14 each week for a number of weeks, w. He writes the expression 20(14)w to find the amount of radioactive substance remaining after w weeks. Autumn starts with 5 milligrams of a radioactive substance. The amount of the substance decreases by 50% each week for a number of weeks, w. She writes the expression (1?0.5)w to find the amount of radioactive substance remaining after w weeks. Use the drop-down menus to explain what each part of Nick's and Autumn's expressions mean. what does 1- 0.5 mean​