Perimeter of triangle is DEF is 73 units.
DG = DH = 11
EH = EI = 16
FI = FG = 9.5
Then sides of triangle is -
DE = DH + EH
DE-= 11 + 16
DE =27
DF = DG + FG
DF = 11 + 9.5
DF = 20.5
FE = FI + EI
FE = 9.5+16
FE = 25.5
The perimeter of the triangle is the sum of all sides of triangle
P = DE+DF + EF
P = 27+20.5 +25.5
P = 73