17) Cele 3 numere sunt egale:
(a+b)/2=c, (b+c)/2=a, (c+a)/2=b
a+c=2b, c=2b-a
b+c=2a, c=2a-b
2b-a=2a-b, adica 3a=3b, a=b
a+b=2c, a=2c-b
a+c=2b, a=2b-c
2c-b=2b-c, adica 3b=3c, b=c
Deci a=b=c
18) (0+1+2+3+4+5+x)/7=10, x=55
19)Se foloseste media ponderata:
(a1x1 + a2x2 +...+anxn)/(a1+a2+...+an)=media ponderata
(4x7+6x8+8x9+4x10+3x4)/(4+6+8+4+3)=200/25=8
20)(2^17 +2^18 +3*2^19)/3=2^17 *(1+2+3*4)/3=15*2^17 /3=5*2^17
21)
(1+2+x)/3=37
3+x=111
xmax=108
xmin=1
