a: \(A=\left(x+1\right)\left(2x+1\right)=199\cdot100=19900\)
b: \(=x\left(y+1\right)+\left(y+1\right)\)
\(=\left(y+1\right)\left(x+1\right)=100\cdot100=10000\)
c: \(=\left(x+z\right)^2-y^2\)
\(=\left(x+z-y\right)\left(x+z+y\right)\)
\(=20\cdot100=2000\)