Answer
$-24$
Work Step by Step
Step 1: $\textbf {u}\cdot(\textbf {v}-\textbf {w})$
Step 2: $\langle -2,1 \rangle\cdot(\langle 3,4 \rangle-\langle -5,12 \rangle)$
Step 3: $\langle -2,1 \rangle\cdot\langle 3-(-5),4-12\rangle$
Step 4: $\langle -2,1 \rangle\cdot\langle 3+5,-8\rangle$
Step 5: $\langle -2,1 \rangle\cdot\langle 8,-8\rangle$
Step 6: $-2(8)+1(-8)$
Step 7: $-16-8$
Step 8: $-24$
