x - (4 - x)

When there is an expression parentheses, and there is no number just before
the parentheses, just a sign, then put a "1" befween the sign and the "(",
like this:

                                                  x - 1(4 - x)

Now, remove the parentheses by using the distributive principle.  That is,
multiply the -1 outside the parentheses by the 4 and also by the -x inside the
parentheses:

                                                   x - 1·4 + x 

(the + before the x is because -1 times -x is +x.

Replace 1·4 with 4
                                                   x - 4 + x

Now put 1's before the x's

                                                  1x - 4 + 1x

Combine the first term, 1x, with the third term, 
which is also 1x, and get 2x.

                                                     2x - 4

Edwin
AnlytcPhil@aol.com