Training Grounds and Mirror Entity

[Hanni]

Training Grounds
Mirror Entity

Just wondering how the interaction works. Does having a Training Grounds in play give an additional 2 mana to the X of Mirror Entity? Like, if I tapped 3 lands (for 3 mana), would my guys be 5/5's or 3/3's?

[(nameless one)]

They would be 5/5 as long as you declare that you're activating Mirror Entity for 5.

[cdr]

You announce what value of X you're activating Mirror Entity for, and then Training Grounds allows you to pay up to (2) less with a minimum of one.

If you announce X=3, you can pay (1), (2), or (3). If you announce X=2, you can pay (1) or (2), etc.