Find 0.001 less than 15.956. a) 15.845 b) 15.856 c) 15.946 d) 15.955

Which is a true statement about an exterior angle of a triangle a. it is formed by two segments that are not sides of the triangle, b. it forms a linear pair with one of the interior angles of the triangle, c. it is complementary to one of the interior angles of the triangle. d. it is formed by two segments that are sides of the triangle.

When 142 is added to a number the result is 64 more times the number my options are 35 37 39 41

How do i simply this expression (quadratic formula basis) on a ti-84 or normal calculator?