Respuesta :

Answer:

30

Step-by-step explanation:

The average of a and b is 20

total a and b = 20 * 2 = 40

The average of a, b, c, and d is 25

total a,b,c and d = 25 * 4 = 100

Total of c and d = 100 - 40 = 60

average of c and d = 60/2 = 30