The value of the missing length is 20
Let the missing length be x
From Parallel lines and transversal theorem, we have that
If three or more parallel lines intersect two transversals, then they cut off the transversals proportionally.
Then, we can write that

∴ 
x = 20
Hence, the value of the missing length is 20
Learn more here: brainly.com/question/24258397
You have the right idea that things need to get multiplied.
What should be done is that the entire fraction needs to get multipled by the lowest common denominator of both denominators.
Let's look at the complex numerator. Its denominators are 5 and x + 6. Nothing is common with these, so both pieces are needed.
The complex denominator has x - 3 as its denominator. With nothing in common between it and the complex numerator, that piece is needed.
So we multiply the entire complex fraction by (5)(x + 6)(x -3).
Numerator: 
= (x+6)(x-3) - (5)(5)(x-3)
= (x+6)(x-3) - 25(x-3)
= (x-3)(x + 6 - 25) <--- by group factoring the common x - 3
= (x -3)(x - 19)
Denominator:

Now we put the pieces together.
Our fraction simplies to (x - 3) (x - 19) / 125 (x + 6)
Answer:
R = sqrt 3 * (V /( pi * h))
V = 62.8
pi = 3.14
h = 15
now we sub
R = sqrt 3 * (62.8 / (3.14 * 15)
R = sqrt 3 * (62.6 / 47.1)
R = sqrt 3 * 1.33
R = sqrt 3.99
R = 1.9 rounds to 2 inches <===
Step-by-step explanation:
Here's your answer to the first problem