Plz i need with this the answer must be rounded to the nearest hundredth

With this question! what is process of elimination? ? p.s. my brothers acc got banned so add his new one @ yamauchiyamyam17

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.

Look at triangle wxy what is the length (in centimeters) of the side wy of the triangle?