Max's car holds 18 gallons of gasoline. driving on the highway, the car uses approximately 2 gallons per hour. let h represent the number of hours max has been driving on the highway. write an expression that shows how many gallons of gasoline max has left after driving h hours.

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.