Step by step
The question
Question: find x when the angles around a point are 120°, 95° and x.
1 Use the angle fact
Angles around a point add up to 360°.
So we add them all and make it 360: 120 + 95 + x = 360.
2 Group like terms
The plain numbers go together.
Now we have 215 + x = 360.
Is x alone now?
Not yet: + 215 is still with x.
How do we remove it?
3 Remove the 215
We want x by itself.
The 215 is in the way.
To remove 215, we take away 215.
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.
215 and − 215 cancel each other.
They make zero.
360 minus 215 is 145.
So x = 145.
The angle x is 145°.
4 Check
Let's check: put x = 145 back and add the angles.
They add up to 360°.
So x = 145 is right!
Let's look back.
First: use the angle fact.
Then: group like terms.
Then: remove the 215.
Last: check.