1. We know A = T, G = C, A + T + G + C = 1, and (A + T)/(G + C) = 0.6
Let x = A = T and y = G = C, then 2x/2y = 0.6 and 2x = 1 - 2y, or (1 - 2y)/2y = 0.6
Solving for y, we get 1 - 2y = 1.2y or 3.2y = 1, so y = 1/3.2 = 0.3125 = G = C.
Solving for x, we get x = (1 - 2y)/2 = (1 - 0.625)/2 = 0.375/2 = 0.1875 = A = T.
Therefore:
A) A + C = 0.1875 + 0.3125 = 0.5
B) A + G = 0.1875 + 0.3125 = 0.5
C) G + C = 2 (0.3125) = 0.625
D) A = T = 0.1875 and G = C = 0.3125