Яку роботу виконують корисні бактерії?

ребят,помогите пожалуйста(

This is part of a letter from Adam,your english pen friend,whom you are going to visit in summer ...As for me,I am crazy about skateboarding and I love rock and pop music.I think my favourite band at the moment is Radiohead.Do you know them?What kind of things do you like doing and what music do you enjoy? Is there anything you particularly want to do while you are here?I guess you will be busy at the language school during the day,but we can do something in the evenings and at weekends.Also,let me know if there are any kinds of food you do not like Write back to Adam In your letter -answer his questions -ask 3 questions about his family and the language school Write 100-140 words Remember the rules of letter writing

в цистерне было 38т керосина.в 1 день израсходовали в 2,4 раза больше керосина,чем во  2.к утру 3-его дня в цистерне осталось 9,1 т керосина.сколько  керосина израсходовали в 1 день? 

давление воздуха составляет 740 мм рт.ст. у подножья горы,а на вершине 340мм рт.ст.высчитайте высоту горы по географии

пожалуйста