a)"You give me 100 dollars", said the brother to his sister,"so that we can have the same sum of money." How many more dollars did the sister have in comparison to the brother in the beginning?
b)Pears are two times more expensive than apples. Which is more expensive: four apples or two pears and by how much?
c)Mark says that just two days ago he was 12 years old and that he will be 15 years old next year. Is Mark right (is it possible)?
a) 200 dollars.
b) Assuming the premise means each pear costs twice what each apple costs, then four apples costs precisely as much as two pears. Otherwise there isn't enough information to be sure which costs more.
c) Yes it is possible: Today is January 1 and Mark's birthday is December 31. Then Mark was 12 years old two days ago on December 30, is 13 years old now, turns 14 years old next December 31 --which is during the same year--, and turns 15 years old at the end of next year.