Substituting a syms with an equation

I have a syms Array:

syms A11 A12 A13 A21 A22 A23 A31 A32 A33 a b c x y z

A=[A11 A12 A13;A21 A22 A23;A31 A32 A33]

.

How do I replace a symbolic variable A11 with an equation:

A11=a*x+b*y+c*z

Answer 1

[Walter Roberson]

subs(A, A11, a*x+b*y+c*z)