вам даны слова: Take place,run (3),be(5) compete!После слов такие цифры!Это значит это слово столько раз повторяется! Текст: In march 1981,the first London Marathon ........... . 7,747 people ....... in it. So,people ......... the London Marathom since 1981. it........42,195 kilometrovs long.

In march 1981,the first London Marathon took place . 7,747 people competed in it. So,people have been running the London Marathom since 1981. it is 42,195 kilometrovs long.

думаю так

In march 1981,the first London Marathon TOOK PLACE . 7,747 people COMPETED  in it. So,people  HAVE BEEN RUNNING the London Marathom since 1981. it IS  42,195 kilometrovs long.

ЦИФРЫ ПОСЛЕ СЛОВ ОБОЗНАЧАЮТ НОМЕР ПРЕДЛОЖЕНИЯ!