Step by step
The question
Question: find x when the angles in a triangle are 48°, 75° and x.
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: 48 + 75 + x = 180.
2 Group like terms
The plain numbers go together.
Now we have 123 + x = 180.
Is x alone now?
Not yet: + 123 is still with x.
How do we remove it?
3 Remove the 123
We want x by itself.
The 123 is in the way.
To remove 123, we take away 123.
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.
123 and − 123 cancel each other.
They make zero.
180 minus 123 is 57.
So x = 57.
The angle x is 57°.
4 Check
Let's check: put x = 57 back and add the angles.
They add up to 180°.
So x = 57 is right!
5 Change the form
We can't type a square root or π.
The calculator gives 57 and more digits.
6 Count the characters
The answer box takes 5 characters.
57 has 2.
It fits.
7 Type it in
We type 57.
Let's look back.
First: use the angle fact.
Then: group like terms.
Then: remove the 123.
Then: check.
Then: change the form.
Then: count the characters.
Last: type it in.