Answer:
580 cm
Step-by-step explanation:
To find the surface area you just need to find the area of every side of the box and add them together.
SO- the equation for this would be
SA (Surface Area) = 2(20 x 10) + 2(20 x 3) + 2(10 x 3)
SA = 2(200) + 2(60) + 2(30)
SA = 400 + 120 + 60
SA = 520 + 60
SA = 580
