Degree of unsaturation (DU) in the following compound is

 
Number of double bonds = 3
Ring = 1
Thus, degree of unsaturation (DU) = 4
$\therefore DU=\frac{2(n_1+1)-n_2}{2}=(n_1+1)-\frac{n_2}{2}$
Where, $n=$  numbers of C-atom
$n_2=$ numbers of H-atom
Molecular formula  $=C_{11}{H}_{16}$
$DU=(11+1)-\frac{16}{2}=4$