Basic solving for $x$

Question

I am doing some really basic chemistry but I am having problems with some of the math involved. Basically I just need help solving $x$ for this question and I think that I am good. $$Ka=X^2/0.500=1.8 × 10^{-5}.$$ According to the textbook the answer is $X=3.0 × 10^{-3}$, so how do I find $X$?

Answer 1

You have $\dfrac{X^2}{0.500} = 1.8\cdot10^{-5}$

$\implies X^2 = 1.8\cdot0.500\cdot 10^{-5}$

$\implies X^2 = 0.90 \;\cdot\;10^{-5}$

$\implies X = \sqrt{9.00 \;\cdot\;10^{-6}}$

$\implies X = 3\cdot10^{-3}$