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