This is the problem:

There are a total of 19 ghosts, witches & scarecrows. The number of witches is 6 more than the number of ghosts. The number of scarecrows is 2 less than the number of witches. How many of each will you find?

I read from one of the posts that you should put the words into variables:

g+w+s=19

How can I put "the number of witches is 6 more than the number of ghost"? Is it like:
w=(6+g)

Then, scarecrows
s=(w-2)

So this is the equation so far:

(6+g)+(w-2)+g=19

What do I do next? Please give as simply as possible explanation, thank you! :D

You've figured out how to write the equations:

g+w+s=19 (Equation 1)
w=(6+g) (Equation 2)
s=(w-2) (Equation 3)


You now have three *independent* equations and three unknowns. That is always solvable.

In this case, I'd recommend trying to use "substitution". Equations 2 and 3 are already in a form that you can substitute for w and s, directly. Try it, one equation at a time and simplify until you have only one variable to solve for. If you have any problems, I'll show you how to solve it.