Дана арифметическая прогрессия (сn), в которой с2 = -9 , с3 = -5 Найдите первый член , разность и сумму первых 8 членов прогрессии .

Решить уравнением!   На изготовления  60  тетрадей двух видов пошло   840  листов бумаги. На каждую тетрадь одного вида требовалось  12 листов, а на тетрадь другого вида  18  листов. Сколько изготовили  тетрадей каждого  вида  ?

Put the verb into the most suitable form, past continuous, past perfect or past perfect continuous 1)John and I went for a walk. I had difficuly keeping up with him because he ............. (walk) so fast. 2) Sue was sitting on the ground. She was out of breath. She.............(run) 3)When I arrived, everybody was sitting round the table with their mouths full. They ......................(eat) 4)When I arrived, everybody was sitting round the table and talking.Their mouths were empty, but their stomachs were full. They ..............(eat) 5) Jim was on his hands and knees on the floor. He....... (look) for his contact lens 6) When I arrived, Kate ..........(wait) for me. She was annoyed with me because I was late and she .......(wait) for a long time 7) I was sad when I sold my car. I......... (have) it for a very long time 8) We were extremely tired at the end of the journey. We .....(travel) for more than 24 hours

помогите с реакцией пожалуйста.
CH---CH+HCN=ЧТО ПОЛУЧАЕТСЯ?

Звук распространяется в воздухе со скоростью 330м/с. Алёша услышал гром через 12 секунд после вспышки молнии. На каком расстоянии от Алёши произошёл разрад молнии.