Answer:
84
Explanation:
The surface of this figure consist of six faces:
two right triangles with legs = 4 and 3 sm;
one rectangle with sides 5 and 6 sm;
one rectangle with sides 3 and 6 sm;
one rectangle with sides 4 and 6 sm.
The surface area of whole figure is the sum of areas of this faces.
-- triangle area
-- rectangle 5x6 area
-- rect. 3x6 area
-- rect. 4x6 area