How to Determine Proton Concentration in a Mixed Solution?

[symbolipoint]

x is the concentration of H₃O⁺, which is equal to the concentration of SO₄^2-. 0.5-x is the concentration of HSO₄^-. We ignore the concentration of water as it is effectively constant.
Your solution to the quadratic equation is incorrect.

(I did not solve it. I only wrote it.)

 

[symbolipoint]

I don't know where this come from.. 0.5 - x and x refers to what concentration..
But i calculate
x = 0.01 +- 0.05$\sqrt2$

Study basic algebra: Algebra 1 and Algebra 2;
then study Elementary Chemistry, and the first or the first AND second semesters of General Chemistry; only then may you understand these topics.