Answer
-18
Work Step by Step
We know that $\langle u_1,u_2 \rangle \cdot \langle v_1,v_2\rangle$ is equal to $u_1v_1 +u_2v_2$. Thus, we find that the dot product of these two vectors is: $$\langle 9,9\rangle \cdot \langle -4,2\rangle \\ (9)(-4) +(9)(2) = -18$$ This is a scalar quantity.