This principle is called Chargaff's rule. In double stranded DNA Thymine is always bound to Adenine while Cytosine is always bound with Guanine. Therefore the percentage of A will always equal the...
Every adenine in DNA will be paired to a thymine. However in RNA adenine is paired to uracil. So no - all else being equal since there is DNA and RNA in a body there will not be equal amounts.