Give an example of a multi step equation for each of the following solutions

Henry is an avid reader, he devours 90 pages in half an hour how many pages has henry read per minute?

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.

Which property was used to simplify the expression? 3c+9 +4c=3c+4c+9