Solve 4x < 12

Step by step

The question

Question: solve 4x < 12.

This is an inequality.

The sign means less than.

1 Remove the 4

4x means 4 times x.

We want just x.

To remove times 4, we divide by 4.

We do it on both sides.

Why both sides?

The sign compares the two sides.

If we change only one side, the answer can change.

4 divided by 4 is 1.

So just x is left.

12 divided by 4 is 3.

So x is less than 3.

2 Show it on a number line

Books also write the answer like this.

It is called interval notation.

A round bracket means the end is not in, like the open circle.

∞ means it goes on for ever.

3 Check

Let's test one number from the answer: 2.

We put it in place of x.

First the left side.

Now the right side.

8 is less than 12.

True!

So the answer works.

Let's look back.

First: remove the 4.

Then: show it on a number line.

Last: check.