Find the Value of each variable (will mark brain list if you do these!!!)

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.

Two rectangular prisms have the same volume. the area of the base of the blue prism is 418 4 1 8 square units. the area of the base of the red prism is one-half that of the blue prism. which statement is true?

Simplify (8x2 − 1 + 2x3) − (7x3 − 3x2 + 1). −5x3 + 11x2 − 2 5x3 − 11x2 + 2 x3 + 2x2 + x3 x3 − 2x2 − x3