find the surface area of each of the faces of the cuboid and cube, add them up and take away the overlap
#total surface area of a solid
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e.g. for the vertical sides of the cuboid at the bottom, you do 5*6 = 30 cm^2 for one side, multiply that because you have two of those sides, to get 60 cm^2
then find the area of another face of the same cuboid, the one that has dimensions 5 cm x 7 cm, to get 35 cm^2 and because you have two of those too, multiply it by 2 which gives 70 cm^2
then the last face pair for that cuboid gives you a total of 84 cm^2 (includes two sides)
add all of those up to get the surface area of the cuboid underneath
do the same process for the cube on top
add those up and then take away 16 cm^2 from that because the side of the cube and the cuboid overlap in the middle