Is there supposed to be a picture??
Answer: 
Step-by-step explanation:
Given
Marcos purchased a sailboat for 
Each year the boat will decrease in value by 
After 1 year it is
after another year it becomes
After 
years it is
First find the side lengths of the box by factoring each area:
12: 1, 2, 3, 4, 6, 12
15: 1, 3, 5, 15
20: 1, 2, 4, 5, 10, 20
Find 3 numbers that both have 2 sides have in common and can multiply to make the areas of the faces:
12: 3 * 4
15: 3 * 5
20: 4 * 5
Sides: 3, 4, and 5
Then multiply to get the volume:
3 * 4 * 5 = 60 units^2
A, B and C working together will finish same piece of work in 10 days
A can do a piece of work in 20 days. That is A is doing the work at a rate of 1 / 20. Therefore
B = 1 / 30
C = 1 / 60
A, B and C working togehter their rate will be added together =
A + B + C = 1 / 20 + 1 / 30 + 1 / 60 = 1 / 10
so they can work together to finish same piece of work in 10 days
