одна швея может выполнить работу за 4 часа, другая -за 8 ч. Успеют ли они выполнить всю работу за 2 и 2/3ч, если будут работать вместе

Приведи подобные слагаемые: 15a-3b+8a-4a-3.6b+b           3y-7x-9y-16y+9y-2x-x -5.2a+6a-6a+15a-b+3b                       -a+x+3x-4.2x+1.3x+2a

Вставьте  there is / there isn't / is there / there are / there aren't / are there, was / there wasn't / was there / there were / there weren't / were there.

1  ..............................................nowhere to sit down...............................................any chairs.

2  ……………………………………  any letters for me yesterday?

3 Twenty years ago..............................................................many tourists here. Now there are a lot.

4  I'm sorry I'm late...............................................................a lot of traffic.

5  'Did you buy any eggs?'    'No,..............................................................any in the shop.'

6  '..............................................a bus from the city centre to the airport?'    'Yes. Every 20 minutes.'

7  '..............................................................many people at the meeting?'    'No, very few.'

8  We didn't visit the museum..............................................................enough time.

9  '..............................................any problems?'    'No, everything is OK.'

 10 'Can we take a photograph?'    'No,..............................................a film in the camera.'

1) 6/7-a+12a/a^2-49, при a= -5

2) x+y/ х; если x/y=0,2    Помогите пожалуйста.