314. Реши уравнения.

1) x - 640 = 921 : 3 => x - 640 = 307 => x = 307 + 640 => x = 947.
2) x : 9 = 2007 : 9 => x = 2007.
3) x * 81 = 729 : 3 => x * 81 = 243 => x = 243 / 81 => x = 3.