Answer: 22% cytosine, 28% each of thymine and adenine
Explanation: Remember the base pairing rules: cytosine always pairs with guanine and adenine with thymine, in equal amounts. With that in mind, you can conclude that since the bases are 22% guanine, they are also 22% cytosine. Since you've still got a 56% that's unaccounted for (to make up 100%), you could divide that by 2 (because you know there are 2 bases left, thymine and adenine, and they are always equal).
Hope this helps,
Lacia :)
