How do i write an accurate (and easy) explicit formula?

Which one ? is the answer and how to find this answer

Will mark determine whether the conjecture is true or false. give a counterexample for any false conjecture. given: points r, s, and t conjecture: r, s, and t are coplanar. a) false; the points do not have to be in a straight line. b) true c) false; the points to not have to form right angles. d) false; one point may not be between the other two.

Multiply: 2.7 × (–3) × (–1.2). a. –9.72 b. –10.8 c. 10.8 d. 9.72