Найти приближённое значение х∙у и х:у, если: х≈ 0,28, у ≈ 3,26.

Пусть x км/ч - скорость велосипедиста, тогда скорость мотоциклиста (x+10) км/ч .
Время, за которое велосипедист проедет весь путь = 120/x часов, а мотоциклист за 120/(x+10) часов.
Составляем уравнение:
120/x - 120/(x+10) = 6  |*x(x+10)
120(x+10) - 120x = 6x(x+10)
120x + 1200 - 120x = 6x^2 + 60x
-6x^2 - 60x + 1200 = 0
-x^2 - 10x + 200 = 0
D = 100 + 800 = 900 = 30^2
x1 = (10 + 30)/-2 = - 20    - исключаем, т.к. скорость не может быть отрицательной
x2 = (10-30)/ -2 = 10 км/ч - скорость велосипедиста
Скорость мотоциклиста = x + 10 = 10 + 10 = 20 км/ч

ответ: 20

1. You need to take a taxi if you want to catch a train.
2. Children should not play with matches.
3. We need to talk about this tomorrow.
4. That morning I had to go to the bank and so I was late for work.
5. He did not have to get up early, he had a vacation,
6, you must get off at the next stop
7. They are bound to help you in this situation.
8. Did they have to wait a long time for the train?
9. You do not need to speak Russian in English lessons.
10. We had to stay at home yesterday, because it was raining heavily,
11. They do not need to come here every day
12. Students will have to stay after school
13. Do we need to prepare reports for the next lesson? Yes.
14. When will he have to answer all the letters?
15. Adult children should take care of their parents.
16. You had to stay after work, did not you?