posted by Maria .
Hydrogen-like ions are those with only one electron such as He+ and Li2+. The Balmer formula for the transitions in these ions can be written as v=Z^2 cR(1/(n_1^2 )-1/(n_2^2 )). Use this formula to calculate the lowest-energy transition in the Lyman and Balmer series for He+ and Li2+.
So use that formula. Post your work if you get stuck.