Well if there are 16% percent adenine, there has to be a complementary 16% thymine.
This makes up 32% of the bacterial DNA out of the 100%. So to find out the percentages for guanine and cytosine, let's subtract 32 from 100.
100-32 = 68% guanine and cytosine.
Since these two are complementary as well, divide 68 by 2 to find the percentages for both guanine and cytosine.
68/2 = 34%
So, in total, there are 16% adenine, 16% thymine, 34% guanine, and 34% cytosine.