The solution would be like
this for this specific problem:
sin 54 degrees = Height/718.0624
Height = (sin 54 degrees)(718.0624) = 580.9 ft
So the height of the balloon is 580.9 ft. I am hoping that this
answer has satisfied your query and it will be able to help you in your
endeavor, and if you would like, feel free to ask another question.
The goal to proving identities is to transform one side into the other. We can only pick one side to transform while the other side stays the same the entire time. The general rule of thumb is to transform the more complicated side (though there may be exceptions to this guideline).
So I'll take the left hand side and try to turn it into 
One way we can do that is through the following steps:

Since we've shown that the left hand side transforms into the right hand side, this verifies the equation is an identity.
Answer:
n=21
Step-by-step explanation:
We must find n.
Remember PEMDAS. First we must do the Parentheses. Lets do distributive property by multiplying a number that is immediately outside the parentheses with each number inside the parentheses. Lets do this one side at a time.
First lets do 5(n - 7). We get 5n - 35
Now 2(n + 14) is 2n + 28
Okay...... now we have 
Now lets do OPPOSITES!!!! We must do the opposite of each thing to both sides.
The opposite of -35 is positive 35. Lets add 35 to both sides. We get:

Now lets do the opposite of 2n which is -2n

this is looking quite nice isnt it..........
The opposite of 3 times n is 3 DIVIDED BY n. So lets divide both sides by 3

amazing.......