Answer:
The time it will take to roof the house if the homeowner helps the roofer is 2.25 days.
Explanation:
The time it takes the homeowner to roof his house is, <em>X</em> = 9 days.
The time it takes the professional roofer to roof the house is, <em>Y</em> = 3 days.
Then if the the homeowner helps the roofer, the time it will take to roof the house is, <em>X</em> + <em>Y</em>.
The work done by the homeowner in 1 day is,
.
The work done by the professional roofer in 1 day is, 
The work done in 1 day if both the homeowner and the professional roofer work together is,
⇒ 
Then the number of days it takes to roof the house if both the homeowner and the professional roofer work together, i.e. <em>X</em> + <em>Y</em> is,
⇒ 
Thus, the time it will take to roof the house if the homeowner helps the roofer is 2.25 days.
Answer:
River Valleys are productive farming areas because they provide fertile land by flooding.
Explanation:
Agriculture developed in river valleys as rivers flooded their banks, making lands around them fertile and provided fresh water for irrigation. Civilizations developed around rivers because their waters provided places to hunt and fish. Rivers brought along with fertile land along with minerals in it for crops to grow. Rivers allowed the early civilizations to engage in agriculture by growing crops like wheat, barley, and vegetables.
It’s b because if you put a ball on the table and it’s unbalanced of course the ball is going to move so unbalance it’s B
Answer:
I would help u but I don't I understand it language