Răspuns :
a+ax2=639
|----|a
|----|----|ax2
1+2=3(partile egale)
639:3=213(a)
ax2=213x2=426
verificare:213+426=639
|----|a
|----|----|ax2
1+2=3(partile egale)
639:3=213(a)
ax2=213x2=426
verificare:213+426=639