The russian-american biochemist phoebus levene was the first to determine that nucleotides may contain one of four different nitrogen-containing bases. levene believed that the nitrogen-containing bases occurred in equal amounts in dna. what is the actual proportion of these bases?

It depends on the specimen

Step-by-step explanation:

The actual proportion of this bases depends a lot on the organism and the molecule, but it is mostly 60-40 and importance of it is that the purines need to be in equal amounts, and the pyramidines as well, so the proportion between purines and pyramidines is mostly 60-40%, but them between adenine and guanine the proportion is 30-30 and between cytosine and thymine should be 20-20.

check above link.

graphically?   well, you graph them both, the solutions is where they both intersect each other, since there are two solutions, meaning they will meet twice, or namely the linear will run into the quadratic curve twice, and where they meet, those x,y coordinates are the solutions to the system.