Answer:
17.33 or 17 1/3
Step-by-step explanation:
(a + b + c + d) / 4 = 8
(a + b + c + d) = 32
((a + b + c + d) + (x + y + z)) / 7 = 12
(a + b + c + d) + (x + y + z) = 84
32 + (x + y + z) = 84
(x + y + z) = 52
Mean of x, y, z:
(x + y + z) / 3 = mean
52 / 3 = mean
17 1/3 = 17.33 = mean
