JAKE LOVES STEAK; TRISH LOVES FISH (EASY)
Jake enjoys steak so much that the probability that he’ll have it for dinner on any given evening is one in three. The favourite dish of his wife, Trish, is fresh fish. The probability that she’ll have it for dinner on any given evening is one in two. Because Jake and Trish always dine together, they’ll never have steak and fish on the same night. On average, how many times in a 30-day month will they be having either steak or fish?