(1) Million of people went to the festival last year. → Millions
(2) I have two thousands five hundreds yen in my wallet. → thousand, hundred
(3) My father began to study English only when he was in the 60s. → his sixties
(4) Picaso is generally regarded as one of the greatest artists of 20th century.
→ the 20th century
(5) It is estimated that about two-third of the world's population will live in cities within the next 35 years. → two-thirds [two third] of
（解答） I was born one year [a year] before World War Ⅱ broke out.
（別解） World War Ⅱ started [began] one year [a year] after I was born.
（解答） The Tale of Genji has been (being) read in meny countries (ever) since its (first) translation into English (appeared) in the 1920s.
（別解） People in many countries have been reading the Tale of Genji since it was first transleted into English in the 1920s.
（解答） A couple, who seemed to be husband and wife in their late sixties, got on the bus.
（別解） A couple [An elderly couple] who seemed to be married and in their late sixties got on the bus.
（解答） Two-thirds of Japan's land [area] [of Japan] is forest [mountain and forest].
（別解） Two-thirds of Japan's land is covered with [by / in] forest.
（解答） The number og young people who are interested in science and technology has been decreasing since the late 1980s [1980's].
（別解） More and more young people have been reluctant [have been less eager] to study science and technology since the late 1980s.
（別解） Because of [Owing to / Due to] the recent typhiin, about three-fifths of this area's apple crop was seriously damaged.
（解答） Twenty-four [Twenty four / 24] hours is very [really] short. It is, in fact [actually / indeed], even shorter especially because you spend nearly [almost] one-third [one third / a third] of it sleeping.
（別解） We feel as if twenty-four hours passes very quickly. Considering (that) we sleep for nearly one -third of it, it actually seems to go by faster.
（解答） According to the newspapers, more than [over] a billion [one billion] people, or (in order words) about one-seventh [one seventh / a seventh] of the world's poupulation , (had) visited [used / accessed] that website by the end of last year.
（別解） The newspaper says (that) by the end of last year, that website was visited by one billion or more people. This means that it was used by about one out of seven people in the world.
（解答） In my early thirties, I quit [quited / left / resigned from] the publishing company (that / which) I had been working for and went to the U.S., where I worked as an intern teacher at an elemetary chool, teaching Japanese culture.
（別解） When I was in my early thirties, I left my job at the publisher where I had worked until then. After that, I went to the U.S. and began to give lectureson Japanese culture as an elementary school trainee thecher.
（解答） Advances in [Development in] communications technology have made it possible (for us) [enables us / allowed us] to send (out) [to dispatch / to transmit / to give] information [(our) messages] simultaneously [at the same time / at once] to millions of people living [who live] in different [various] parts of the world.
（別解） The advance of communications technology makes it possible for us to send information simultaneously to millions of people living in various countries in the world.