Question

If a species contains 23% A in its DNA, what is the percentage of guanine it would contain?

Answer 1

Edwin Chargaff discovered that A and T are present in equal quantities, and C and G are present in equal quantities. Is that much clear?

Answer 2

A=T
and G=C or 2G
then
100-A+T = 2G
100-23+23=2G
100-46=2G
54=2G
G=27%