Solve 4/5 = x/20

Step by step

The question

Question: solve 4/5 = x/20.

Two fractions are equal.

1 Cross multiply

When two fractions are equal, we can cross multiply.

These two are equal.

Work out the multiplications.

Let's swap the two sides, so x is on the left.

2 Remove the 5

5x means 5 times x.

We want just x.

To remove times 5, we divide by 5.

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.

5 divided by 5 is 1.

So just x is left.

80 divided by 5 is 16.

So x = 16!

3 Check

Let's check: put 16 in place of x.

First the left side.

Now the right side.

Both sides are 4/5.

So x = 16 is right!

Let's look back.

First: cross multiply.

Then: remove the 5.

Last: check.