Angles on a line 3x and 2x

Step by step

The question

Question: find x when the angles on a straight line are 3x and 2x.

1 Use the angle fact

Angles on a straight line add up to 180°.

A straight line is half a turn.

So we add them all and make it 180: 3x + 2x = 180.

2 Group like terms

The x terms go together.

Now we have 5x = 180.

3 Remove the 5

5x means 5 times x.

We want just x.

To remove times 5, we divide by 5.

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.

5 divided by 5 is 1.

So just x is left.

180 divided by 5 is 36.

So x = 36.

4 Check

Let's check: put x = 36 in each angle.

Now add all the angles.

They add up to 180°.

So x = 36 is right!

Let's look back.

First: use the angle fact.

Then: group like terms.

Then: remove the 5.

Last: check.