The 20th visitor will be the first to get both the key chain and the bumper sticker, I found this out by finding the least common multiple, or LCM, you do this by writing out the multiples of both 4 and 10, 4 8 12 16 20..... and 10 20 30... then you find the smallest number that both 4 and 10 have in common. I hope this helps, sorry if it doesn't.
370
You first have to divide 225 by 45 and then multiply by 74
Answer:
Part A. At least 6 hours
Part B. In less than 2.5 hours Elijah will be behind Mercedes
Part C. In more than 2.5 hours Elijah will be ahead Aubrey
Step-by-step explanation:
D = distance
v =speed
t = time
Formula connecting D, v and t:

Part A.
Steve's speed: 
Distance: at least 21 miles
Time: unknown, so
![3.5\cdot t\ge 21\\ \\35t\ge 210\ [\text{Multiplied by 10}]\\ \\t\ge \dfrac{210}{35}\\ \\t\ge \dfrac{30}{5}\\ \\t\ge 6](https://tex.z-dn.net/?f=3.5%5Ccdot%20t%5Cge%2021%5C%5C%20%5C%5C35t%5Cge%20210%5C%20%5B%5Ctext%7BMultiplied%20by%2010%7D%5D%5C%5C%20%5C%5Ct%5Cge%20%5Cdfrac%7B210%7D%7B35%7D%5C%5C%20%5C%5Ct%5Cge%20%5Cdfrac%7B30%7D%7B5%7D%5C%5C%20%5C%5Ct%5Cge%206)
It would take Steve at least 6 hours to walk at least 21 mi on Day 1.
Part B.
Mercedes's speed: 
Elijan's speed: 
Elijan's Distance walked:
miles
Mercedes's Distance walked:
miles
Time: x hours
Mercedes is 2 miles ahead, so

Elijan will be behind when

In 2.5 hours Elijan will catch up Mercedes, and in less than 2.5 hours Elijah will be behind Mercedes.
Part C.
Aubrey's speed: 
Elijan's speed: 
Elijan's Distance walked:
miles
Aubrey's Distance walked:
miles
Time: x hours
At the beginning of Day 3, Elijah starts walking at the marker for Mile 42, and Aubrey starts walking at the marker for Mile 42.5.

Elijan will be ahead of Aubrey when
![D_E>D_A\\ \\42+3.2x> 42.5+3x\\ \\3.2x-3x>42.5-42\\ \\0.2x>0.5\\ \\2x>5\ [\text{Multiplied by 10}]\\ \\x>\dfrac{5}{2}\\ \\x>2.5\ hours](https://tex.z-dn.net/?f=D_E%3ED_A%5C%5C%20%5C%5C42%2B3.2x%3E%2042.5%2B3x%5C%5C%20%5C%5C3.2x-3x%3E42.5-42%5C%5C%20%5C%5C0.2x%3E0.5%5C%5C%20%5C%5C2x%3E5%5C%20%5B%5Ctext%7BMultiplied%20by%2010%7D%5D%5C%5C%20%5C%5Cx%3E%5Cdfrac%7B5%7D%7B2%7D%5C%5C%20%5C%5Cx%3E2.5%5C%20hours)
In 2.5 hours Elijan will catch up Aubrey, and in more than 2.5 hours Elijah will be ahead Aubrey.
Answer:
B.
Step-by-step explanation: