Поготите пожалуйста!!!Рассчитайте объём кислорода в 150 л кислородно-гелеевой смеси, если объёмная доля гелия равна 94%

у меня тема арифметическая прогрессия

не могу понять вот это задание:

дано: а1=-0,3 а7=1,9 найти S5-?

помогите пожалуйста)

найдите сумму всех положительных элементов одномерного массива

Вставьте необходимые предлоги: A tourist took a taxi ... the nightclub ... the hotel where he was staing. a) in/ up b) from/before c) in/to d) at/to e) from/to
2.Дополните предложение: I try to ... standing in a gueue while shopping. a) avoid b) prefer c) like d) insist e) refuse
3.Закончите предложение: I don't like standing in long ... a) buses b) lessons c) queues d) wainting e) crowds
4.Дополните предложение: He is good ... reports and projects. a) in writing b) at writing c) on writing d) with writing e) to write
5.Выберите лишнее: a) Berlin b) Venice c) Melbourne d) Holland e) Paris
6.Дополните предложение: She has paints on her clothes because she ... the room. a) has been painting b) had been painting c) was painted d) has been painted e) had been painted

7. Дополните предложение: The porters at the stations are usually busy carring ... to the rain. a) passengers b) platform c) queues d) luggage
8.Выберите правильный вариант вопроса. Nearly ten years. My house is really beatiful. a) How long did you have in your house? b) How long did you lived in your house? c) How long were you lived in your house? d) How long have you lived in your house? e) How long have you being lived in your house?                    помогите пожалуйста..

с помощью рычага, груз, массой 200 кг подняли на высоту 20 метров. КПД=80%. Нужно найти работу