Răspuns:
notam m=masa,d=dulap
15m+9d=3600
3(5m+3d)=3600
5m+3d=3600:3=>5m+3d=1200
5m=3d
3d+3d=1200=>6d=1200=>d=1200:6=>d=200 lei costa un dulap
3·200=5m=>600=5m=>m=600:5=>m=120 lei costa o masa
verificare
15·120+9·200=1800+1800=3600
15 × m + 9 × d = 3600 | : 3
5 × m = 3 × d
5 × m + 3 × d = 1200
3 × d + 3 × d = 1200
6 × d = 1200
d = 1200 : 6
d = 200
5 × m = 3 × 200
5 × m = 600
m = 600 : 5
m = 120
