[newgeezer]

I would appoint 5 new justices to outvote them and make their presence useless.

You'd have to get rid of five in order to appoint five more.

Or, like FDR, you could try and convince Congress to increase the number from nine to, say, fifteen.

[TexasFreeper2009]

exactly, I would increase the number which is allowed.

In fact the number of judges has been different many times throughout history.