I am taking the same test! ;)
1. RbF --> Rubidium Fluoride
Change fluorine to fluoride
2. CuO --> Copper (II) Oxide
Change oxygen to oxide. Oxide has a charge of -2. Since no subscripts are written, it means they have the same opposite charge. So, we use Copper (II).
3. (NH₄)₂C₂O₄ --> Ammonium Oxalate
NH₄ is ammonia, but we change it to ammonium for poly atomic ions.
I hope this helps!