Isaacson's purpose is: O to inform the reader about traditional art; his tone is
formal.

O to persuade the reader to buy traditional art; his tone
is formal.

O to entertain the reader with humorous traditional
stories; his tone is informal.

O to convince the reader to create traditional art; his
tone is informal.

21 balloons is the story of professor william sherman's travels.

in 1883, he set off from san francisco for a balloon ride over the pacific and was found a month later floating with 21 balloons in the atlantic ocean. this seemed an astounding feat and everyone wanted to know what had happened.    

professor sherman was loyal, however, and said he would tell his tale first to the western american explorers club in san francisco, of which he was a member. this built up suspense for several chapters before he began to tell of the wonders of his adventures and the amazing island of krakatoa, an island which had just been blown up by a volcano.  

the residents of krakatoa are all millionaires who live under a "gourmet government" of their own devising. we get to see all the incredible adventures that creative people with unlimited resources would create according to the author.

by explaining that it took the same total time to travel by plane as it did by train

the answer would be " she kept on going till she got to the north."

good luck! hope i : )