Acookie factory uses 1/4 of a bag of flour in each batch of cookies. the factory used 3 bags of flour yesterday. how many batches of cookies did the factory make?

First of all, you need to compare the two statements. That will be;
1/4= 1 batch
3=Y
Y is the unknown number of batches. So we need to find Y. Next, cross and multiply. 3 will multiply 1 to give 3 and Y will multiply 1/4 to give 1/4Y. That will be;
1/4Y=3
1/4 Y is the same as Y/4. So you have;
Y/4=3
3 is the same as 3/1
Y/4=3/1
Cross and multiply. Y will multiply 1 to give Y and 3 will multiply 4 to give 12. That will be;
Y=12
3 bags will make 12 batches of cookies. Hope that helped. Have a nice day