Question

How do you solve `\frac { 7} { n + 3} = \frac { 3} { 9}`?

Answer 1

Simply cross multiply.

Explanation:

As you can see in my explanation we first start off by cross multiplying:

`9*7=63` and `3(n+3)=3n+9`

We then subtract the `9` to get `3n` alone:

`63-9=54`

Then we simply divide by `3` to get `n` alone:

`54/3=18`

Therefore, our answer is `n=18`.

However, if this is true, when you cross multiply again, they should be the same number.

`7*9=63`
`18+3=21*3=63`

They check out, so this answer is valid and correct.