There is a lot to go over here. Unfortunately it looks like you got a lot incorrect. I'll focus on two problems. Hopefully these examples below will help correct the other mistakes.
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Problem 7)
We have the starting value be 20 and the ending value be 11. Subtract the values: (end)-(start) = 11 - 20 = -9. The negative indicates we have a drop or decrease.
We'll focus on the positive version of this number, so 9. Divide this value over the starting amount 20 to get 9/20 = 0.45 = 45%
So going from 20 miles to 11 miles is a decrease of 45%
Answer to problem 7 is: 45%
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Problem 13)
An increase of 300% means we added 3 times the original amount onto the original amount.
We take 300% of 25 to get 3*25 = 75
Which is then added onto 25 to get 25+75 = 100
Answer to problem 13 is: 100
I'm not sure if this is the easiest way of doing this, but it surely work.
Let the base of the triangle be AB, and let CH be the height. Just for reference, we have

Moreover, let CH=y and BC=z
Now, AHC, CHB and ABC are all right triangles. If we write the pythagorean theorem for each of them, we have the following system

If we solve the first two equations for y squared, we have

And we can deduce

So that the third equation becomes

(we can't accept the negative root because negative lengths make no sense)
Answer:
in triangle BCD
relationship between base and hypotenuse is given by cos angle
cos 71=b/h
cos71=BD/BC
cos71=67/x
x=67/cos71=205.8ft.
the length of BC to the nearest tenth of a foot is 206ft.
Answer:
2
Step-by-step explanation:
2/2+6=7