In the formula [ Cu(NH3)6]2+ what is oxidation no of Cu

Dear student

The oxidation state of NH_{3 =} 0
Let oxidation state of Cu is X.
So the oxidation state of Cu in [Cu(NH₃)₆] is :
   X + 6 * 0 = +2
   X = 2
So oxidation state of Cu is +2.