Angles in a triangle 2x, 3x, 4x

Step by step

The question

Question: find x when the angles in a triangle are 2x, 3x and 4x.

1 Use the angle fact

The three angles in a triangle always add up to 180°.

So we add them all and make it 180: 2x + 3x + 4x = 180.

2 Group like terms

The x terms go together.

Now we have 9x = 180.

3 Remove the 9

9x means 9 times x.

We want just x.

To remove times 9, we divide by 9.

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.

9 divided by 9 is 1.

So just x is left.

180 divided by 9 is 20.

So x = 20.

4 Check

Let's check: put x = 20 in each angle.

Now add all the angles.

They add up to 180°.

So x = 20 is right!

Let's look back.

First: use the angle fact.

Then: group like terms.

Then: remove the 9.

Last: check.