для изготовления сплава взяли золото и серебро в отношении 2:3 .Определите сколько кг каждого металла в слитке этого сплава массой 7,5кг ПОМОГИТЕ ПОЖАЛУЙСТА

Упр. 37. Раскройтескобки, употребляяглаголыводномизвремен: Present Simple, Present Continuous, Present Perfect, Present Perfect Continuous.

1. Her children (to be) in the yard. They (to play) football now. They (to play) it since ten o'clock.

2. She (to speak) English well. She (to study) it for five years. Listen! She (to speak) English to her teacher.

3. His son just (to return) home. He (to be) dirty. He (to play) volley-ball.

4. Where David (to be)? - He (to be) in the library. He (to work) there at the moment. — How long he (to be) there? - He (to work) for three hours.

5. Why she (to look) tired? - She (to work) all night.

6. Since when they (to wait) for us? - They (to wait) for half an hour. We (to be) late.

7. My sister (to drive) a car. She (to learn) to drive for two months.

8. Beth (to be) busy this morning, hasn't she? - Yes. She already (to write) some letters and (to interview) four people.

9. Julia already (to return) home. She always (to come) home at this time. She (to do) her lessons. She (to do) them since three o'clock.

10. My baby (to sleep) at the moment. My baby (to sleep) for two hours.

11. Peter (to write) letters now. He (to write) since seven o'clock. He (not to finish) writing yet.

12. What they (to do) now? - They (to discuss) a very important problem. They (to discuss) it for two hours; but they (not to reach) the agreement yet.

13. I never (to suppose) that he can cook. He (to be) in the kitchen now. He (to cook) for an hour and he already (to prepare) some tasty dishes.

14. The weather (to be) fine today. There (to be) no clouds in the sky, the warm wind (to blow). Thesun (toshine) sinceearlymorning.

Какой металл - цинк или ртуть - способен вытеснить водород из соляной кислоты? Составте уравнение возможной реакции. Назовите продукты реакции.