The vertical lines are absolute values, the number in between them, if negative turns positive.
Like every quadratic equation

where 

we can factor out 

And find the two solutions

In this case, the solutions are

If you know that
are the solutions to the quadratic equation

then you can factor the poynomial as

So, in this case, you have

Answer: 50.0
Step-by-step explanation:
1. Add 45+55=100
2. Divide 100 by 2 =50
3. Add a decimal after 50.0
Answer:
-12
-18
Step-by-step explanation:
-n+8=20
-n=20-8
n=12
-36=n-18
-n=-18+36
n=-18