Răspuns :
(72+s-40)-(30-10+5)=50:2
(72+s-40)-(20+5)=25
(72+s-40)-25=25 /+25
72+s-40=50 /+40
72+s=90
s=90-72
s=18
(72+s-40)-(20+5)=25
(72+s-40)-25=25 /+25
72+s-40=50 /+40
72+s=90
s=90-72
s=18
(72+s-40)-(30-10+5)=25.
(72+s-40)-25=25
Inlocuim 72+s-40 cu "a"
a-25=25
a=50
72+s-40=50| +40
72+s=90
s=90-72
s=18.