Răspuns:
12. (a+b+c+d+e+f):6=21
(m+x+y+z):4=61
a+b+c+d+e+f=21*6=126
m+x+y+z=61*4=244
(a+b+c+d+e+f+m+x+y+z):10=
=(126+244):10=370:10=37(media aritmetica)
13.
(a+b+c+.......+x):100=?
[19*8+11*18+(100-30)*15]:100=
=[178+198+70*15]:100=
=[1050+376]:100=
=1426:100=14,26
