Simona's music book includes 50 piano tunes, of which 7 are by bach, and 18 are by mozart.

if simona chooses a tune at random, what is the probability that it is either by bach or by mozart?

i think there was a typo. you wrote pat brings 3 quarts of ice-cream to the party. each serving of ice-cream is 1 6 quart. how many total servings of ice-cream does pat bring to the party? i think the bold is supposed to be 1/6. so 1 quart of ice cream = 6 servings. 6 * 3 = 18.