(x+3)(4+2xyz)

(4+2xyz)

*   (x+3)

--------------

    12 + 6xyz

+  4x + 2x²zy

---------------

(2x²yz + 6xyz + 4x + 12)

I'll get the same answer but it the working might look different.

$$(x+3)(4+2xyz)\\\\
=x(4+2xyz)+3(4+2xyz)\\\\
=4x+2x^2yz+12+6xyz$$