2/3 is the same as 4/6, 8/12, 16/24. You can multiply both the top and bottom of the fraction by the same number and get an equivalent fraction.
4/8 is the same as 8/16 1/2. 1/2 is possible because you can divide both 4 and 8 by 2.
Hope this helps! feel free to ask if this doesn't make sense!
