NH₂OH(aq) + H₃AsO₄(aq) → HONH₃⁺(aq) + H₂AsO₄^–(aq)

K_c = K_a(acid)/K_a(conjugate acid) = (6.0×10^–3)/(1.1×10^–6) = 5500 > 10 so the reaction goes to completion

NH₂OH(aq) + H₂AsO₄^–(aq) → ← HONH₃⁺(aq) + HAsO₄^2–(aq)

K_c = K_a(acid)/K_a(conjugate acid) = (1.0×10^–7)/1.1×10^–6 = 0.091 < 10 so the reaction is an equilibrium

The third reaction has a much smaller equilibrium constant so is not worth considering

acid/base