How to replace every non-0 number with the number in that place added to another number - no loops

Say I have a matrix I want to loop in a cell in the matrix and change that particular cell to itself added to another number. I have tried to explain mself better with inputs and expected output in the code.

A=[1 0 3;4 5 0;8 0 9] % matrix
B=-7 %additional number
% idk what code i need but every non-zero number in that matrix must be added to b 
C=[-6 0 -4; -3 -2 0; 1 0 2] % what I expect the output to be

Answer 1

[Stephen23]

I think it is neater to only define the index once:

>> X = A~=0;
>> A(X) = A(X)+B
A =
  -6   0  -4
  -3  -2   0
   1   0   2

Answer 2

[Andy]

A(A~=0) = A(A~=0) + B