Answer:
one of the girls read 5 books, and the other read 7 books
Step-by-step explanation:
if 6 is the number of half the books that the girls read, the total should be 12, since half of 12 is 6.
each girl has to read a number of books that equal 12 when added together, they do not have to be the same number, but they do have to be two numbers apart.
therefore the solution is 5, and 7, since 5 + 7 = 12 and the numbers are apart by a difference of two.
