flexed budgets

a firm uses flexed budgets. the flexed budget for last period was based on 100 activity and showed direct costs of 50000. the actual direct cost were compared with flexed to show the following
actual direct cost 45000 variance 4500 adverse
what was the actual activity as a percent for last period?

I calculated this answer as 45000-4500=40500/50000×100= 81%
but i am confused should i subtract the variance or just simply divide 45000 by 50000