15. Doug Upp can shovel coal at the rate of 16 tons per day. His brother, Sid, can e rate of 16 tons per day. His brother, Sid, can shovel 10 tons per day.

a) Define a variable for the number of days Doug has shoveled. Then write an expres

umber of days Doug has shoveled. Then write an expression for the number of

tons Doug has shoveled. X=# days

b)

Three days later, Sid joins Doug, and both shovel together. Write an expression for the num

days Sid has been shoveling in terms of your variable in part a. Then write an expression for the

number of tons Sid has shoveled.

C) Write an equation stating that the total number of tons Doug and Sid have shoveled is 100. Then

solve the equation to find out how many days Doug dug when they have shoveled this much coal.

Q.1 dr. frank needs to choose 3 students from her advanced biology course to attend a conference in hawaii. the course has 40 students. which of the following methods could dr. frank use to choose a simple, random sample of 3 students? select all that apply. 1 dr. frank could have the students line up from shortest to tallest, then use her birthdate, 2/5/39, to select 3 students from the line (the 2nd student, the 5th student, and the 39th student). 2. dr. frank could upload her class roster into a spreadsheet and use a ranom-number generating function to produce 3 random numbers. the students whose names are located in the rows with these 3 numbers on the spreadsheet would be chosen. 3. dr. frank could choose the students with the 3 highest grades in the class. 4. dr. frank could count to three, then the first students to come to the front of the classroom and grab a golden ticket from her hand would be selected. 5. dr. frank could ask all students to write their name on a card, place all of the cards in a hat, shake the hat, and then pull 3 cards out from the hat. the students whose names appear on those 3 cards will be selected. 6. dr. frank could ask for volunteers to go to the conference, then choose the first 3 students who raise their hands. q2. now, choose one of the methods that you did not select and explain why this method would not result in a simple, random sample: