im sorry but i cant see the orange cuboid number at the bottom but i'll consider its a 5cm (i hope its correct)
firstly, you have to find the area of EACH faces then just add them togeher
whereas, diagram A
9 x 9 = 81 ( 1 face)
* since cube has 6 faces then just multiply by 6 then
answer: 486 cm²
for diagram B
front and back faces: 2(5x7)
left and right faces: 2(15x7)
top and bottom: 2(5x15)
answer: 430cm²
then compare between 486 and 430
answer should be 486 > 430
hope this helps :)
