If you had a sequence that was 32% thymine, how would the percentages be formed?

You know that your total amount equals to 100%
Complementary bases are usually present in equal amounts so if you have 32% thymine then you have 32% of adenine
32% times two equals 64%
100% - 64% = 36%
This means that you have 36% left for cytosine and guanine
36% / 2 = 18%
So you have 18% guanine
18% cytosine
36% thymine
36% adenine