An energy of 24.6eV is required to remove one of the electrons from a neutral helium atom. The energy in ($eV$) required to remove both the electrons from a neutral helium atom is

When an electron is removed from neutral helium atom,it becomes hydrogen like atom. Ionisation energy of hydrogen like atom is given by

 $E_{\text{ion}}=+Z^{2}Rhc$

For $He,Z=2,Rhc=13.6eV$ 

Energy required to liberate second electron from helium is 

$E_2=E_{\text{ion}}=(2{)}^{2}13.6\mathrm{eV}=54.4\mathrm{eV}$

Energy required to remove both the two electrons from helium nucleus is $E_1+E_2=24.6+54.4\mathrm{eV}=79\mathrm{eV}$