100% total of all 4 bases and Guanine and Cytosine need to have 1:1 ratio and Adenine and Thymine need to have 1:1 ratio (This is the Chargaff's rules I think)
6% Guanine must also mean 6% Cytosine
6 + 6 = 12 100 - 12 = 88 88/2 = 44
So 44% of Adenine and 44% of Thymine