a+b+c+d=861
1) nr.care il succed pe 29 sunt 30 si 31
deci a=30
b=31
30+31+c+d=861
c+d=861-61
c+d=800
c:d=7
c=800-d
inlocuim
800-d:d=7
800-d=7d
8d=800
d=100
c:100=7
c=700
Verificare: 30+31+700+100=861
2) !____________! x
!____________!__!__! x+2
!____________!_________! 2x
S=x+(x+2)+2x
S=4x+2
3)!_______!______! a
!_______! a:2
!_______!----------!-----------!
notam a:2 cu x
3x-2x=43
x=43
a=2x=43x2
a=86
b=43x3
b=129
129-86=43