Răspuns:
a, b, c = suprafetele arate in fiecare din cele 3 zile
S = a + b + c
a = (2/6)*S
b = (1/6)*S
C = 21
-----------------------
a = (1/3)*(a+b+c) |*3
b=(1/6)*(a+b+c) |*6
c=21
-----------
3a = a + b + 21
6b = a + b + 21
------------
2a = b + 21
5b = a + 21 -> a = 5b - 21
------------
2*(5b-21) = b + 21
10b - 42 = b + 21
10b - b = 21 + 42
9b = 63
b = 63/9 = 7
a = 5*7 - 21 = 35-21 = 14
--------------
S = 14 + 7 + 21 = 42
Terenul are 42 hectare
