Step by step
The question
Question: solve 2x + 9 = 5x.
1 Get x on one side
There is x on both sides.
We want x on one side only.
So we remove the 2x from the left side.
To remove 2x, we take away 2x.
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.
2x and − 2x make zero.
Cross them out.
5x − 2x = 3x.
Now we have 9 = 3x.
Let's swap the two sides, so x is on the left.
2 Remove the 3
3x means 3 times x.
We want just x.
To remove times 3, we divide by 3.
We do it on both sides, so they stay equal.
3 divided by 3 is 1.
So just x is left.
9 divided by 3 is 3.
So x = 3!
3 Check
Let's check: put 3 in place of x.
First the left side.
Now the right side.
Both sides are 15.
So x = 3 is right!
Let's look back.
First: get x on one side.
Then: remove the 3.
Last: check.