The answer is: 1 : 20
We first need to identify a basic ratio for green counters. This is started by comparing them to orange counters, as there are eight orange counters for every green counter.
We then find out that for every 2 orange counters, there are 5 blue counters. This helps us because we can use this fact to deduce that if you have 8 orange counters, you would have 4 groups of 2 orange counters. Since every 2 orange counters gives you 5 blue counters, if you had 4 groups of 2 orange counters, you would have 20 blue counters (4 * 5). Since there were was only one green counter for every 8 orange counters, this means there’s only 1 green counter for every 20 blue counters.
Hope this helps.