Answer:
G=21 %
T= 29 %
A= 29 %
Step-by-step explanation:
Since C only binds to G, you have the same amount of C and G, so G is 21 %.
100 % minus 42 % ( 21 % C plus 21 % G=) equals 58 %.
So the other 58 % is made of T and A. Since T only binds to A , the half of the extra 58 % is T and the other half is A. Therefore 29 % is T and 29 % is A