The "dot product" of two vectors has several different formulas.
Since you are given the x- and y-coordinates of both vectors a and b, we can apply the formula
a dot b = ax*bx + ay*by, where ax=x-component of vector a, by=y comp of vector b, and so on.
So, for the problem at hand, ax * bx + ay * by becomes
3(-2) + (-8)(-6) = -6 + 48 = 42 (answer). Note that the dot product (or "scalar product" is itself a scalar.
