15 point question i have no idea 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.

Write an inequality for this description. - one fourth of the opposite of the difference of five and a number is less than twenty.

#7. m is the midpoint of pq, the diameter of the circle o is 13in. and rm = 4in. find pm find pq