Energy of 

${\displaystyle n^{th}}$ state in hydrogen is same as to 3nth${\displaystyle 3n^{th}}$ state in Li++${\displaystyle L{i}^{++}}$.
3 to 1 transition in H would give same energy as the ${\displaystyle 3\times 3}$ to ${\displaystyle 1\times 3}$ i.e. , 9 to 3 transition in  Li++.Li++