The first step is to calculate what fraction of the counters that Rob has.
Add all the portions together to find the total: 5+6+7= 18 Rob has 5 out of the 18, or 5/18, or 0.278
Next, do the same for the end ratio: 7+9+8= 24 and Rob has 7/24, or 0.292
By comparing his beginning portion (0.278) to his end portion (0.292) it is clear that he has a greater portion of the total counters. Given that the problem states that the number of counters stays the same, Rob must have more counters than he started with.
