Răspuns :
s-stiloul
c-cartea
s+c=17920
c=28×s÷100
inlocuiesti si rezulta
s+28s÷100=17920 /×100
100s+28s=1792000
128s=1792000
s=14000=>c=17920-14000
c=3920
c-cartea
s+c=17920
c=28×s÷100
inlocuiesti si rezulta
s+28s÷100=17920 /×100
100s+28s=1792000
128s=1792000
s=14000=>c=17920-14000
c=3920
s + c = 17920
c = 28/100 * s
s + 28s/100 = 17920
100s + 28s = 1792000
128s = 1792000
s = 1792000 : 128
s = 14 000 stiloul
c = 28/100 * 14 000
c = 3920 lei cartea
c = 28/100 * s
s + 28s/100 = 17920
100s + 28s = 1792000
128s = 1792000
s = 1792000 : 128
s = 14 000 stiloul
c = 28/100 * 14 000
c = 3920 lei cartea