Y=5x would give them the money they earn after all the car washes. In order to calculate when they make a profit, you could use:
5x>75
So, you can divide 75 by 5 to get that they need to wash at least 15 cars to earn all the money they spent on setup, and to make a profit, they must wash more than that.
Answer: 
Step-by-step explanation:
We have the following expression:

In order to work in a better way this expression, let's call
and
and rewrite:

Now, we know
. Let's apply it here:


Simplifying:

According these trigonometric identities, we have:


Then:

Writing again the actual values:

Finally:

Answer:
81 square inches
Step-by-step explanation:
9*9 = 81
Answer: Find the volume of cone, whose radius is 8 cm and height is 5 cm. Thus, the volume of the cone is 334.93 cm3.
Answer:
???
Step-by-step explanation: