Incepem cu ultima egalitate
4c = d:4
4c = 1/4×d |×4 (inmultim toata balanta cu 4)
16c = d
=> d = 16c
c+d = 170
c+16c = 170
17c = 170
c = 170:17
c = 10
c+d = 170 => 10+d = 170
d = 170-10
d = 160
Verificare :
40 = 160:4
40 = 40
b-4 = 4c
b-4 = 40
b = 44
a+4 = b-4
a+4 = 40
a = 36
