Angles on a line 130 and x

Step by step

The question

Question: find x when the angles on a straight line are 130° and x.

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: 130 + x = 180.

2 Remove the 130

We want x by itself.

The 130 is in the way.

To remove 130, we take away 130.

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.

130 and − 130 make zero.

Cross them out.

180 minus 130 is 50.

So x = 50.

The angle x is 50°.

3 Check

Let's check: put x = 50 back and add the angles.

They add up to 180°.

So x = 50 is right!

Let's look back.

First: use the angle fact.

Then: remove the 130.

Last: check.