I need help

 

You have one square that is 11 m on a side.  Its area is 11² 

 

You have four quarter circles which is equivalent to one whole circle with radius 5.5 m.  Its area is 3.14 x 5.5²  

 

Figure up those two areas and subtract the circle from the square. 

 

121 square meters – 94.985 square meters  =  26.015 square meters, rounded is 26.02 square meters 

_.

 

Working backwards reveals that the second guest probably used 3.1416 for the value of pi.  That explains the difference of 0.05 in the two answers, since the first guest disclosed that s/he was using 3.14.