(A rectangular brick measurses 6cm by 9cm by 20 cm and has a mass of 2.563 kilograms.)
What is the brick's surface area in square centimeters, and square centimeters?
Why do the same calculation twice? Did you copy the question correctly?
There are two sides with 6 x 9 cm^2 area, two sides with 6 x 20 cm^2 area, and two sides with 9 x 20 cm^2 area. Compute and add up the areas.
You don't need the mass to do this problem.