Here I think the given data was LM=7,MN=6 and perimeter was given by 16m
As we know perimeter is the sum of all the sides
so Perimeter=LM+MN+NL
NL=Perimeter-(LM+MN)
NL=16-7-6
NL=3
By Heron's formula
Area=sqrt(s(s-a)(s-b)(s-c)).
where s=perimeter/2
so s=16/2=8
area=sqrt(8(8-7)(8-6)(8-3))
area=8.94427191
after rounding off
area=9
