Answer: x = 5
Step-by-step explanation: In this problem, we want to get x by itself on one side of the equation. Since we have 21 + x, in order to get x by itself, we must subtract 21 from the left side of the equation and when we subtract 21 from the left side of the equation, we must also subtract 21 from the right side of the equation in order to keep our equation balanced.
So on the left, +25 and -25 cancel eachother out and on the right, 26 - 21 simplifies to 5 so x = 5. To check our answer, we plug 5 back in for x in the original equation and we get 21 + (5) = 26 or 26 = 26 which is a true statement so we know our answer is correct.