help with (3,1,3)#(2,3,4)

Maybe you mean

$\begin{bmatrix} 3 && 1 && 3 \\ \end{bmatrix} \cdot \begin{bmatrix} 2\\ 3 \\4 \end{bmatrix} =\begin{bmatrix} 3*2+1*3+3*4 \end{bmatrix}=\begin{bmatrix} 21 \end{bmatrix}$

See here for Matrix Multiplication

https://goo.gl/qVkz5B

Thanks, Melody....

This could also indicate that we want to take the dot product of the vectors

(3, 1, 3)   and ( 2, 3, 4)   =

We just multiply  like components and add these products....so we have

3*2  + 1*3  + 3*4   =

6   +  3   +   12  =

21