The amount of Cytosine plus Guanine is 40%. What would be the amount of Adenine?

30%

Explanation:

Considering that the amount of Cytosine added to the amount of Guanine is 40%, that explains that Cytosine and Guanine each equal to 20%.

Now, the remaining bit is 60%. Since Adenine and Thymine both equal the same, that would mean: 60/2 = 30.

Cytosine and Guanine pair together and will always be equal to one another. The same goes for Adenine and Thymine. (A=T, C=G)

Always remember that you want it to total up to 100% at the end.

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