Step by step
The question
Question: solve x/(x + 4) = 3/5.
Two fractions are equal.
1 Cross multiply
When two fractions are equal, we can cross multiply.
These two are equal.
Work out the multiplications.
2 Open the brackets
The 3 in front of the bracket multiplies every part inside.
So we write 3 times each part.
Work out each multiplication.
3 Get x on one side
There is x on both sides.
We want x on one side only.
So we remove the 3x from the right side.
To remove 3x, we take away 3x.
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.
3x and − 3x make zero.
Cross them out.
5x − 3x = 2x.
Now we have 2x = 12.
4 Remove the 2
2x means 2 times x.
We want just x.
To remove times 2, we divide by 2.
We do it on both sides, so they stay equal.
2 divided by 2 is 1.
So just x is left.
12 divided by 2 is 6.
So x = 6!
5 Check
Let's check: put 6 in place of x.
First the left side.
Now the right side.
Both sides are 3/5.
So x = 6 is right!
Let's look back.
First: cross multiply.
Then: open the brackets.
Then: get x on one side.
Then: remove the 2.
Last: check.