P ( Y or B) = P(Y) + P(B) - P (Y and B) → 0.6 = P(Y) + P(B) - 0 (1)
P ( Y or G) = P(Y) + P(G) - P (Y and G) → 0.8 = P(Y) + P(G) - 0 (2)
P(Y) + P(B) + P(G) = 1 (3)
Add (1) and (2), and we have
1.4 = 2P(Y) + P(B) + P(G) → 1.4 - 2P(Y) = P(B) + P(G) (4)
Subbing (4) into (3), we have
P(Y) + 1.4 - 2P(Y) = 1 simplify
-P(Y) = -0.4 → P(Y) = 0.4
So using (1)
0.6 = 0.4 + P(B) - 0 → P(B) = 0.2
And using (2)
0.8 = 0.4 + P(G) - 0 → P(G) = 0.4
And the probability of landing on blue or green =
P(B or G) = P(B) + P(G) - 0 = 0.2 + .0.4 = 0.6
