posted by blah .
Three vectors are given by = 1.0 + 3.0 + -4.7, = 2.0 + 2.0 + -4.0, and = 3.0 + -4.2 + -4.0. Find (a)·( × ) and (b)·( + ).
You seem to have omitted the unit vector designation (usually written i, j and k). What you have written are not vectors, but sums of numbers.
What does the equals sign in front of each trio of numbers represent?
One doesn't take cross products of three vectors.