it will be 8.25 hope this helped
First, take off 4 feet of Stacy's rope, which is 19. (23-4=19). Then, divide 19 by 3. It should equal 6.3...
Each curve completes one loop over the interval

. Find the intersections of the curves within this interval.

The region of interest has an area given by the double integral

equivalent to the single integral

which evaluates to

.
Answer: 
This is the same as writing 7*Ln( e^(2x) + 10) + C
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Explanation:
Start with the equation 
Apply the derivative and multiply both sides by 7 like so

The "multiply both sides by 7" operation was done to turn the 2e^(2x) into 14e^(2x)
This way we can do the following substitutions:

Integrating leads to

Be sure to replace 'u' with e^(2x)+10 since it's likely your teacher wants a function in terms of x. Also, do not forget to have the plus C at the end. This is a common mistake many students forget to do.
To verify the answer, you can apply the derivative to it and you should get back to the original integrand of 