Please please help i have three questions left for this lesson

1. convert. simplify your answer and write it as a proper fraction or as a whole or as a mixed number. 4oz=_ pounds 2. find 1/3 of 66

Just tell me how to set up the equation.

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.