Step by step
The question
Question: find x when the angles on a straight line are 112° and x.
1 Use the angle fact
Angles on a straight line add up to 180°.
So we add them all and make it 180: 112 + x = 180.
Is x alone now?
Not yet: + 112 is still with x.
How do we remove it?
2 Remove the 112
We want x by itself.
The 112 is in the way.
To remove 112, we take away 112.
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.
112 and − 112 cancel each other.
They make zero.
180 minus 112 is 68.
So x = 68.
The angle x is 68°.
3 Check
Let's check: put x = 68 back and add the angles.
They add up to 180°.
So x = 68 is right!
4 Change the form
We can't type a square root or π.
The calculator gives 68 and more digits.
5 Count the characters
The answer box takes 5 characters.
68 has 2.
It fits.
6 Type it in
We type 68.
Let's look back.
First: use the angle fact.
Then: remove the 112.
Then: check.
Then: change the form.
Then: count the characters.
Last: type it in.