Consider the fission reaction ${^{236}_{92}U}→X^{117}+Y^{112}+n+n$ i.e. two nuclei of same mass number 117 are found plus two neutrons. The binding energy per nucleon of X and Y is 8.5 MeV whereas of $U^{236}$ is 7.6 MeV. The total energy liberated is

20 MeV

$ \text{Energy released is difference of energy of parent nuclei and daughter nuclei}$

$ \text{Binding Energy of }_{92}U^{236} = 236\times 7.6 = 1793.6 MeV$

$ \text{Binding Energy of }X^{117} and Y^{117} = 234\times 8.5MeV = 1989 MeV$

$\Rightarrow 1793.4 = 1989 + Q$

$\Rightarrow Q = - 195.6MeV$