How do you solve #50- x - ( 3x + 2) = 0#?

#50-x-(3x+2)=0#

Open the brackets and simplify. The product of #-# and #+# is #-#.

#50-x-3x-2=0#

#48-4x=0#

Add #4x# to both sides.

#48=4x#

Divide both sides by #4#.

#12=x# or #x=12#

#50 - x - (3x + 2) = 0#

Expand the bracket.
You know that when there is no number outside the bracket it is 1. However, you can see the minus sign just outside the bracket (on the left), so that means the bracket is being multiplied by -1.
#-1 xx (3x + 2)# should give you#-3x - 2#

The bracket then disappears since you've multiplied it.
Your equation now looks:
#50 - x -3x -2 = 0#

Simplify any like terms.
There are two different like terms;
50 and -2,
AND
-x and -3x

#50 -2 = 48#
and
#-x - 3x = -4x#

You've now simplified the equation and left with:
#-4x + 48 = 0#

Send 48 to the right-hand side and it will become -48.
#-4x = 0 - 48#
#-4x = -48#

Now to find #x#, you need to move -4 to the right-hand side. Currently -4 is being multiplied by #x#, so when you send it to the right-hand side, -4 will be divided by -48.
#x = ((-48) / -4)#
#x = 12# is your final answer

Just to check whether it equals to zero:
#50 - x - (3x + 2) = 0#
#50 - 12 - (3 xx 12 + 2) = 0#
#50 - 12 - 38 = 0#
#0 = 0#
YES!!