Надо вычислить массу железа полученного из 100г Fe3O4 путем восстановления углем, если выход Fe 70% от теоретического. Помогите пожалуйста

Напишите сумму, разность, произведение и частное двух алгебраических выражении: (a+b) и (3-c)

замени каждое число суммой разрядных слагаемых. 308,30806,308004

как выглядели летние и зимние жилища первобытных людей?

Put the sentences into negative form and make questions.

He became a great painter, (not)

Our French lesson began at 9 o'clock. (When?)

Sally wrote a dictation yesterday. (not)

The cat lay on the bed. (Where?)

John knew her address. (not)

Tim lost his money in the shop. (Yes/No?)

Ann understood the teacher very well. (Who?) 

Jack bought a new computer last week. (What?)

We went to the circus two days ago. (not)

Our group had a party last week. (not)

Sally bought a new dress, (not) 

Tom lost his bag. (Where?)

Jane forgot about my birthday, (not)

Sam wrote a long letter. (Yes/No)

Bob knew about this house, (not)

Ashley brought a big cake. (When?)

Alice understood him very well. (Why?)

Fred saw a horrible dog. (Yes/No)

Jack found a beautiful stone. (Where)

George lay on a small sofa. (not)

Fill in the proper verb in Past Simple

What (the teacer, say) ........................................?

(you,not,tell) ................................... us your name.

Ann (not, know) ....................... the other girl's name.

I think you (do) ..............................the wrong thing.

The student (stand) .......... up when the teacher arrived.