a- nr de pizza comandate in prima zi
b - a doua zi
c- a treia zi
a+b+c=165 (1)
a+b=105 (2)
b+c=117 (3)
adunam relatiile (2) si (3)
a+b+c+b=222
(a+b+c)+b=222
165+b=222
b=222-165
b=57
a+57=105 (din relatia 2)
a=105-57
a=48
57+c=117 (din relatia 3)
c=117-57
c=60
Verif 48+57+60=165
Garfield a comandat 48 de pizza in prima zi, 57 in a doua si 60 in a treia zi.