How to find concentration of a solution from pH (without calculator)

Here is question from Uplearn A-Level Chemistry Course.

Hypobromous acid has a Ka of 2.24x10^-9 at room temperature. What is the concentration of hypobromous acid in a solution that has a pH of 6.56?

Here is the formula for Ka:
Ka = [H+][A-]/[HA]

I know how to do this question with a calculator but my mathematics lets me down finding the hydrogen ion concentration from the pH without a calculator. Is this even a question that could appear in the IMAT?

Thanks for your help! Great website!

This is fantastic! Thanks Reza!

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