a). Watermelons = 1/4 (2/3) = 2/12 = 1/6 of the fruits 

b). Oranges = 3/4 (2/3) = 6/12 = 1/2 of the fruits
Since 1/2 of fruits = 39 oranges,
number of apples = 1/3 (39 x 2) = 26 #