Emily has 250 books. if frank were to double the number of books that he now owns, he would have more than emily has.

X - the number of Frank's books.
y - the number of Emily's books.

Emily has 250 books:
y = 250 

If Frank were to double the number of books that he now owns (2x), he would have more than Emily has (y):
2x > y
2x > 250
x > 250/2
x > 125

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)