Change from the active into the passive.Помогите с упражнением пожалуйста 1.Tchaikovsky...

Question

Change from the active into the passive.Помогите с упражнением пожалуйста
1.Tchaikovsky used many folk-tunes in his compositions.2. The agronomist has introduced new methods of work in agriculture. 3. The lecturer showed his students a recently devised apparatus. 4. We all must look after the children. 5. The population of France gave the Russian delegation a hearty welcome. 6. The gardener asked me to help him in the garden.7. The students of this group are translating the English text. 8. They finished their work earlier than usual. 9. We have sent him a telegram. 10. The students were discussing the problem at 6 o’clock yesterday. 11. You must buy a new English dictionary.

Answer 1

Many folk-tunes were used in Tchaikovsky's compositions.
New methods of work in agriculture has been introduced by the agronomist.
A recently devised apparatus was shown by the lecturer
Children must be looked after
The Russian delegation was given a hearty welcome by the population of France
I was asked to help in the garden by the gardener
The English text is being translated by the students of this group 
Their work was finished earlier than usual
The telegram was sent to him (by us)
The problem was discussed among students at 6 o'clock yesterday
A new English dictionary must be bought (by you)