Answer:
13% cytosine
37% thymine
Step-by-step explanation:
Chargaff's rule states that the DNA always has a 1:1 ratio of purine bases (the cytosine and thymine to pyrimidine bases (guanine and adenine).
If there is 13% guanine, then there must also be 13% of cytosine (since G pairs with C)
The total of guanines and cytosines is 26%, meaning the total of A + T is 100% - 26% = 74%. That means there are 74/2 = 37% of thymine.