Hi! I'm happy to help!
To solve this, we have to divide the 18 pounds, in 1/8 portions. We do this with division. To make this problem easier to solve, we need to turn it into a multiplication problem (opposite of division). To still make the problem correct, we have to take the opposite of one of our numbers. Let's take 1/8, and turn it into 8, now we have the problem:
18×8=
Now all we have to do is multiply:
18×8=
144
He can make 144 croissants!
I hope this was helpful, keep learning! :D