Solving an Equation

Here is a typical equation: 3X - 5 = 27

To solve this equation, you could just use guess-and-check. You would just guess at values of X and keep changing your guess until you got the right answer. But this takes a lot of time! Here's a better way:

Remember in the second grade when your teacher asked you to fill in the box in a problem like this:
4 + = 10
In algebra all we do is use a letter, like "X" instead of a box:

4 + X = 10

This equation asks you: What number equals 10 when you add 4 to it?

The answer to this question is 6, because 4 + 6 = 10.

Here are some simple equations:
EquationThe question it asksThe
answer
Reason
X + 5 = 15 If you add 5 to my number you get 15. What is my number? X = 10 Because
10 + 5 = 15
X - 13 = 13 If you subtract 13 from my number you get 13. What is my number? X = 26 Because
26 - 13 = 13
3X = 18 If you multiply my number by 3, you get 18. What is my number? X = 6 Because
3 times 6 = 18
X/4 = 5 If you divide my number by 4, you get 5. What is my number? X = 20 Because
20/4 = 5

How about something more complex, like this equation:
2X - 5 = 11

Here's how you solve an equation of this type:
  1. Cover up the "2x" with your finger (I'll use a box): - 5 = 11
  2. Now solve for the value of the "box":
    = 16 because 16 - 5 = 11
  3. Now look at what is in the : 2X = = 16
  4. Now solve the above easy equation:
    X = 8, because 8 times 2 = 16
Here are some other equations, and how you would solve them:
Equation Step 1:
Cover up the term
with X in it
Step 2:
Solve for the boxed term
Step 3:
Look at what's in the box and solve for it
3X + 1 = 7 = 6
because 6 + 1 = 7
X = 2, because
3 times 2 = 6
X/2 - 1 = 3 = 4
because 4 - 1 = 3
X = 8, because
X/2 = 4