найдите углы правильного двенадцатиугольника

составьте схемы, отражающие строение атомов:1) азота 2)неона 3)натрия

ПОЖАЛУЙСТА ПОМОГИТЕ, ПРОШУ

упростите рациональное выражение а)(1/а+1/b+1/с)abc б)(a/b+b/c+c/a)*ab/c

Байдарка в 10:00 вышел из пункта А в пункт В, расположенный в 15 км от А. Пробыв в пункте В 4 часа, катер отправился назад и вернулся в пункт А в 18:00. Определите (в км/час ) собственную скорость катера, если известно, что скорость течения реки 2 км/ч. желательно решение)

Прошу помочь с легким заданием. 

     The call from Mr Hill came when John was taking a shower. John’s wife Laura answered it. When John    (A1) the room a minute later, she   (A2)  . “The doctor says Tommy  (A3)  a good sleep last night,” Mr Hill said. “He  (A4)  worse today than he  (A5)  yesterday. But please  (A6)  too much. The doctor  knows  what he is doing”. “Yes,” said Laura, “good…” and then    (A7)  because John  was trying to tell her something.

     “If you   (A8)  on a plane this morning, you    (A9)  there in the evening,” he said.

     “Yes,” she replied. “Please  thank your wife for helping Tommy. Good buy.” She put down the telephone and looked round the room.

A1   1) was entering         2) entered            3) had entered                 4) has entered

A2   1) is still speaking     2) still spoke       3) was still speaking       4)still speaks

A3   1) does not have        2) did not have    3) had not had                4) has not had

A4   1) is                           2) was                  3) has been                     4) had been

A5   1) had been               2) has been           3) was                            4) were

A6   1) are not worrying   2) will not worry  3) does not worry         4) do not worry

A7   1) had stopped           2)stopped             3) has stopped              4) stops

A8   1) are getting             2) is getting          3)  will get                    4) get

A9   1) is arriving              2) arrive                3) will arrive                 4) are arriving