a+b+c = 28
b = 3×a+3
c = 3×b+3
a |___|
b |___|___|___|+3
c |___|___|___|___|___|___|___|___|___|+3+9
avem 13 segmente egale +3 +3+9 = 28
28 - (3+3+9) = 28 - 15 = 13
13 : 13 = 1 (un segment egal)
a = 1
b = 3×1+3 = 6
c = 9×1+12 = 21
Verificare:
1+6+21 = 28
a = 1
b = 6
c = 21
