I know the correct answer is B (it was on the page) but how do I get there?

20 da is equal to a. 2,000 cm. b. 2 m. c. 20,000 cm. d. 20,000 mm

Negative 5 1/12 + negative 4 1/4 + 6 3/4

Let f(x) = 3 − x . find the average rate of change of f(x) from x = a to x = a + h and simplify your answer so that no single factor of h is left in the denominator.