Hello, could someone please help me and explain how to do this:)

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.

Find the unit rate for: 75% high-fiber chimp food to 25% high -protein chimp food.

Robin spent 25% more time on his research project than he had planned he’s been an extra h ours on the project which of the following expressions could represent the number of hours rob actually spent on the project