Curl operates on a vector field, and A is such a field.
A=<xz,-y²,2x²y>. Let A₁=xz, A₂=-y², A₃=2x²y.
Curl uses the grad operator ∇=<∂/∂x,∂/∂y,∂/∂z> and the vector product:
∇᰽A=<∂A₃/∂y-∂A₂/∂z,-∂A₃/∂x+∂A₁/∂z,∂A₂/∂x-∂A₁/∂y>=<2x²,-4xy+x,0>.
Now we plug in (1,1,2):
Curl(A)=<2,-3,0>.
Magnitude |Curl(A)|=√(2²+3²+0²)=√13=3.61.