a) ma = (7 x 2 + 15 x 3)/ (2 + 3) = 59/5 = 11,8
b) ma = (7 x 7 + 15 x 3)/(7 + 3) = 94/10 = 9,4
c) ma = (7 x 9 + 15 x 11)/(9 + 11) = 228/20 = 11,4
d) ma = (7 x 14 + 15 x 6)/(14 + 6) = 188/20 = 9,4
e) ma = (7 x 8 + 15 x 17)/(8 + 17) = 311/25 = 12,44
f) ma = ( 7x 31 + 15 x 19)/(31 + 19) = 502/50 = 10,04
g) ma = (7 x 9 + 15 x 6)/(9 + 6) = 153/15 = 10,2