Solve 3(x - 4) = 9

Step by step

The question

Question: solve 3(x − 4) = 9.

1 Remove the 3

The 3 multiplies the whole bracket.

Easy way: remove the 3 first.

To remove times 3, we divide by 3.

We do it on both sides.

Why both sides?

The = sign means both sides are the same amount.

If we change only one side, they are not the same any more.

3 divided by 3 is 1.

So just the bracket is left.

9 divided by 3 is 3.

Now we have x − 4 = 3.

We don't need the bracket any more.

2 Remove the − 4

We want x by itself.

The − 4 is in the way.

To remove − 4, we add 4.

We do it on both sides, so they stay equal.

− 4 and + 4 make zero.

Cross them out.

3 + 4 = 7.

So x = 7!

3 Check

Let's check: put 7 in place of x.

We get 9, the same as the right side.

So x = 7 is right!

Let's look back.

First: remove the 3.

Then: remove the − 4.

Last: check.