my GPA this semester so far is 3.5
taking that into account, my cumulative GPA is 3.8
If I get an A -, which is equivalent to a 3.7, does my cumulative GPA increase or decrease?

on one hand, 3.7 < 3.8, so it should drag it down
on the other hand, 3.7 > 3.5, so it raises this semester's GPA