First, you have to find the lowest common multiple of the two denominators of the fractions, which is 7 and 9. So, the LCM is 21. Now, list out the multiples of 21 below 50, which will give you only 21 and 42. Now, you try both numbers.leo_mums wrote:There were fewer than 50 exercise books left at a school bookshop on Monday.

On Tuesday, 1/7 of the exercise books were sold.

On Wednesday, one book fewer than 4/9 of the remaining exercise books were sold.

On Thursday, 2 books more than 3/7 of the remaining exercise books were sold.

How many exercise books did the bookshop have on Monday?

21:

21*6/7=18

18*5/9=10

10+1=11

11*4/7=6 2/7

6 2/7-2=4 2/7

So, that means that you can't use 21.

42:

42*6/7=36

36*5/9=20

20+1=21

21*4/7=12

12-2=10

Ans:42