Răspuns :
creion= c
stilou= s
4c+4s= 72
4(c+s)=72
c+s= 18
s= 12+c
c+12+c= 18
2c= 18-12
2c= 6
c= 6:2
c= 3
s= c+12= 3+12= 15
3c+5s= 3 x 3+ 5 x 15 = 9+75= 84
creion= c
stilou= s
4c+4s= 72
4(c+s)=72
c+s= 18
s= 12+c
c+12+c= 18
2c= 18-12
2c= 6
c= 6:2
c= 3
s= c+12= 3+12= 15
3c+5s= 3 x 3+ 5 x 15 = 9+75= 84