Okay let's take this step by step. Let's start with "21 = 6 - x - 4x".
First off, I'm going to flip this equation around, since it tends to be easier to solve equations when the variable is on the left.
6 - x - 4x = 21
Next, I'm going to combine my like terms. Seeing how 21 is all by its lonesome on the right, I just have to worry about the left side. Since 6 is the only number without a variable on the left, I'll leave it alone. But I'll go ahead and combine -x and -4x.
6 - 5x = 21
(When a variable is alone, it's simply a shorter way of writing 1x.)
Next I'm going to subtract both sides by six.
6 - 5x = 21
-6 -6
-5x = 15
(6 and -6 cancel each other out.)
Finally I'm going to divide 15 by -5.
-5 / -5 x = 15 / -5
x = -3
The two -5s cancel each other out, and we find out x equals -3.
Next let's handle "1 + p + 5 + p = 2"
First, we'll combine like terms.
6 + 2p = 2
Then we'll subtract both sides by 6.
6 + 2p = 2
-6 -6
2p = -4
Finally, we'll divide both sides by 2.
2/2 p = -4/2
p = -2
We find that p equals -2.
Now we'll finish off with "2(z - 1) = 16".
First, we have to distribute 2 to both z and -1. When distributing, we just multiply the term(s) in the parenthesis by the term(s) outside them.
z(2) -1(2) = 16
2z -2 = 16
Then we'll add 2 to both sides.
2z -2 = 16
+2 +2
2z = 18
Lastly, we'll divide both sides by 2.
2/2 z = 18/2
z = 9
And in our last problem, we find that z equals 9.
(I underlined all the answers for you.)
+16 
