Answer: Vaughn collected 72 pieces of litter.
Step-by-step explanation: The equation is correct. You get that by going backwards through the information in the story.
Vaughn's number is x.
Piper is 1/4 x
Sara is Piper +12 So (1/4 x)+12
Dom is Sara -15. So (1/4 x) -3
Add all Piper, Sara & Dom on one side of the equation.
The other side is the Vaughn's amount minus 9 because it says he picked up 9 more than the others combined. So x-9 equals the amount of the other three combined.
The three 1/4 x add to 3/4 x
Skipping to the solution:
x - 3/4 = 12 -3 +9
1/4 x = 18 Multiply both sides by 4
x = 72
1/4 x is 18, Piper's number.
Use that to calculate the Sara and Dominique.