Exa-6.5   
The freq. corresponding to the longest wavelength of balmer is 4.572474e+014 & First longest wavelength  of Lymann is 2.469000e+015.
The sum of which s equal to 2.926248e+015
The freq. corresponding to 2nd longest wavelength was found out to be 2.926223e+015
.Hence Ritz combination principle is satisfied.