Step by step
The question
Question: 3 less than a number is 10.
Find the number.
1 Find what we know
What do we know?
3 less than a number is 10.
What do we want?
The number.
2 Name the unknown
We don't know the number.
So we call it x.
3 Write the equation
Change the words to math, one part at a time.
Less than turns the order around.
We start with a number, then take away 3.
So the equation is x − 3 = 10.
Now we solve it.
Careful: x − 3 is not the same as 3 − x.
The order matters when we take away.
4 Remove the − 3
We want x by itself.
The − 3 is in the way.
To remove − 3, we add 3.
We do it on both sides, so they stay equal.
− 3 and + 3 make zero.
Cross them out.
10 + 3 = 13.
So x = 13!
5 Answer the question
The number is 13.
6 Check
Let's check in the story.
Put 13 in the story: 3 less than 13.
It makes 10, like the story says.
So the answer is right!
Let's look back.
First: find what we know.
Then: name the unknown.
Then: write the equation.
Then: solve it.
Then: answer the question.
Last: check.