 ## Algebra rules

 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:
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 ⬜ + 1 = 7 ⬜ = 6 because 6 + 1 = 7 3 X = the ⬜ which is 6,
so X = 2, because 3 X 2 = 6
X/2 - 1 = 3 ⬜ - 1 = 3 ⬜ = 4 because 4 - 1 = 3 X/2 = the ⬜ which is 4,
so X = 8, because 8/2 = 4

Now, here's a problem for you:         4 X + 7 = 19       X = _______