план описания.  Водоема в Москве СРОЧНО

Помогите решить,пожалуйста.
Log6(x^2+7x)=Log6(8x+42).
Log3(21-x)=log3(x-7)+2.
Log2(x^2-4x)=log2(6x-16).

41. Hello! How are you? A) I’m an engineer. B) Pleased to meet you. C) Fine, thanks. And you? 42. Would you like some crisps? A) No, please. B) No, thanks. C) No, okay. 43. What does she do? She … . A) does secretary B) is a secretary C) is cooking 44. We are late for the football match. A) Hurry up! B) Yes, I’m playing football. C) What date is it? 45. Excuse me, what’s the time, please? A) I’m late. B) I don’t have time. C) Sorry, I don’t have a watch. 46. Good morning, madam! Can I help you? A) Yes, please! B) Yes, I like it! C) No, I don’t. 47. Let’s stay at home and watch TV tonight. A) OK! What’s on? B) Let’s go! C) Do it! 48. I didn’t pass my English exam. A) Do you? B) Well, I do. C) I’m sorry! 49. Good-bye! A) Fine, thank you! B) Bye! C) Hello! 50. What is the weather like today? A) Yes, I like it. B) Yes, it is. C) It is fine

Что такое (нескінченні границі) киньте сылку

Пристани А и Б расположены на реке , скорость течения которой на этом участке равна 4 километра в час. Лодка проходит от А до Б и обратно без остановок со средней скоростью 6 километров в час. Найдите собственную скорость лодки/