The events of having a major flaw and of having only minor flaws are mutually exclusive. Therefore P(major flaw or minor flaw) = P(major flaw) + P(only minor flaw = 0.15 + 0.05 = 0.20.
The events of having a major flaw and of having only minor flaws are mutually exclusive. ThereforeP(major flaw or minor flaw) = P(major flaw) + P(only minor flaw = 0.15 + 0.05 = 0.20.