At first glance, you would think that you would convert a 12 point scale grade point average to a 4 point scale simply by dividing by three. This would make logical sense because 12/3 = 4. This would give you a GPA of 2.9 on the 4.0 scale, which is just under a B average.
However, this is not the correct conversion. In order to make the correct conversion, you need to use a chart rather than simply doing basic math. You can find charts for this at this link and this link. These charts show us that an 8.7 GPA on a 12 point scale is roughly equal to a 3.2 GPA on a 4 point scale.