12*x+6000=40200 

помогите 

Помогите, пожалуйста, решить генетические ряды.  

Fe2O3 -> Fe3O4 -> FeO -> Fe -> FeCl3 -> Fe(OH)3 -> Fe2O3   

приведите примеры влияния деятельности человека на биосферу.

It (has been around / has been since)1760. Its seven floors are packed (with / in) toys, toys and toys! Here you can buy any type of ( toy/ a toy) you like/ There are ( thousands of / thousands) cars , computer games, soft toys, teddy bears, dolls, and what not.