1. The girl was looked for everywhere.
2. The boy wasn't listened to.
3. The patients were looked after well.
4. Our address was asked for.
5. These papers were looked throught this morning.
6. My brother will be given English lessons.
7. I have been shown an intresting magazine.
8. He was told everything by his friend.
9. The famous lecturer was warmly greeted by the students.
10. A huge plant has recently been built in the town of N.
11.The work must be finished by tomorrow.
12. When I fell ill, the doctor was sent for.
13. Helen was shown the nearest way to the theatre.
14. His patient was given some good advice.
15. I have been told the news by Mary.
16. The little boy was looked at with interest.
17. The paper was examined attentively.
3 т -100%
х т -7,8%
х=3*7,8/100=0,234 т=234 кг масса железа
ответ: 234 кг масса железа в 3 т руды