Metoda grafica:
a |___|
b |___|___|___|
c |___|___|___|___|___|___|___|___|___|
c - a = 9 segm. egale - 3 segm. egale = 6 segmente egale = 18
18 : 6 = 3 (un segment egal)
a = 3
b = 3×3 = 9
c = 9×3 = 27
Metoda algebrica:
b = 3×a
c = 3×b ==> c = 9×a
c - b = 18
9×a - 3×a = 18
6×a = 18
a = 18 : 6
a = 3
b = 3×3 = 9
c = 9×3 = 27