How do I solve these problems

The problems I have in my math book are:

22. The volume of a rectangular box is 280 in^3. Its dimensions are 4 in x (n+2) in x (n+5) in. Find the value of n. Use v=lwh.

23. You're building a rectangular pool. The area of the bottom is 90 ft^2, and the length is 3 more than 2x the width. (The book doesn't tell me how deep the pool is.) What are the pool's dimensions?

24.If the area of a triangle is 110 ft^2, and side A = 2x+2, while side B = x, what is x?

I've been trying to do these problems for ages, and I'm nowhere closer to getting the answers. Any help will be greatly appreciated.

The volume of a rectangular box is 280 in^3. Its dimensions are 4 in x (n+2) in x (n+5) in. Find the value of n. Use v=lwh.

4(n + 2)(n + 5) = 280

(n + 2)(n + 5) = 70

solve the quadratic...

n^2 + 7n + 10 = 70

n^2 + 7n - 60 = 0

(n + 12)(n - 5) = 0

n = - 12 [extraneous, the measure of a side must be positive]
or
n = 5

check

4(7)(10) = 280 in^3

One problem at a time...

If you have been trying for ages, and getting nowhere with problems this easy...go to your teacher now !

Show your work !

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# 22 )))
V = L W H = 280 in ³
( 4 ) in. • ( n + 2 ) in. • ( n + 5 ) in. = 280 in.³
....................in the meantime, let's drop the units of measurement.
4 • ( n + 2 ) • ( n + 5 ) = 280
....................multiply the terms in one parenthesis to
....................each of the terms in the other parenthesis;
4 • (n)(n) + (n)(5) + (2)(n) + (2)(5) = 280
4 • ( n ² + 7n + 10 ) = 280
4n ² + 28n + 40 = 280
....................subtract 280 from both sides of the equation;
...........................remember that performing the same mathematical operation
...........................on both sides of the equation would still maintain its equality.