Calculate the hydronium ion concentration (M) showing all steps of a solution formed by 300ml of 3M HCl with 100ml of 2M KOH. Please help!?

Initial number of moles of H₃O⁺ ions = (3 mol/L) × (300/1000 L) = 0.9 mol

1 mole of KOH completely dissociates in aqueous solution to give 1 mole of OH⁻ ions.
Initial number of moles of OH⁻ ions = (2 mol/L) × (100/1000 L ) = 0.2 mol < 0.9 mol

Equation for the reaction :
H₃O⁺(aq) + OH⁻(aq) → 2H₂O(l)
Mole ratio H₃O⁺ : OH⁻ = 1 : 1
Obviously, OH⁻ ions completely reacts, and H₃O⁺ ions are in excess.

No. of moles of OH⁻ ions reacted = 0.2 mol
No. of moles of H₃O⁺ ions reacted = (0.2 mol) × 1 = 0.2 mol
No. of moles of H₃O⁺ ions left unreacted = (0.9 - 0.2) mol = 0.7 mol
Final volume of the solution = (300 + 100) ml = 400 ml = 0.4 L

Final H₃O⁺ ion concentration = (0.7 mol) / (0.4 L) = 1.75 M