Math Help - undoing logs in chemistry

1. undoing logs in chemistry

It may seem easy but i have an exam soon and i have forgotten how to undo logs!
This is for chemistry and involves the equation to find pH.

pH = -log [concentration of Hydronium Ions]

or in more maths terms

y = -log x

I can't really believe i have forgotten this but i just cant do it. I need 'x' to be the subject.

Thanks.

2. For pH you use log to the base 10, the inverse of this is raising the log to the power of 10
i.e.
$10^{\text{Log}_{10}(x)}=x$

$\text{pH}=-\text{Log}_{10}[\text{H}_3\text{O}^{+}]$
$-\text{pH}=\text{Log}_{10}[\text{H}_3\text{O}^{+}]$
$[\text{H}_3\text{O}^{+}]=10^{-\text{pH}}$