Question 980025
Length 16.5m; breadth11m; height 5.5m

2 walls are 16.5 m long x 5.5 m high.  Their area is 90.75 m^2*2=181.5m^2
2 walls are 11m  long (the breadth) x 5.5 m high.  Their area is 57.5 m^2 *2 =115 m^2

Sum is 296.5 m^2 area.
It is important not to multiply the three terms together, because that would give volume.  Area means square and requires two numbers to be multiplies.  Height is common to both, but the other variable is length for 2 walls and breadth for the other 2 walls.