You can only do this kind of multiplication crisis cross.
1. Your problem is 2/4 over 8/16
2. 2 and 16 have 2 in common. 2 divided by 2 is 1 and 16 divided by 2 is 8
3. 4 and 8 have 4 in common. 4 divided by 4 is 1
8 divided by 4 is 2
4. Now your problem is 1/1 times 2/8
5. 1 times 2 is 2
6. 1 times 8 is 8
7. If you don't like this method you can also reduce in the end. 2/8 can still be reduced into 1/4 because the reduce number that I picked was smaller
I really hope this helps
