Answer
$1$
Work Step by Step
The dot product of two vectors $\mathbf a= \langle a_1,a_2,a_3 \rangle$ and $\mathbf b= \langle b_1,b_2,b_3 \rangle$ is $a_1b_1+a_2b_2+a_3b_3$.
So for $\mathbf a= 2i+j=\langle 2,1,0 \rangle$ and $\mathbf b= i-j+k=\langle 1,-1,1 \rangle$, $$\mathbf a \cdot \mathbf b =2(1)+1(-1)+0(1)=2-1+0=2-1=1.$$
