2. A clothing store is having a "Start the summer" sale. Alex pays $37 for two T-shirts and a pair of sunglasses (the sunglasses cost $13).
(a) Model Alex's purchase with an equation.
(b) Solve the equation to find the price of one T-shirt.

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.