у*120/100=690. у=690*100/120=575. x*115/100=575. x=575*100/115, x=500 lei pretul initial. 6) a+b=600, a=600-b, 696-600=96. a*20/100+b*10/100=96, 20a+10b+9600. 20(600-b)+10b=9600. 12000-20b+10b=9600. 10b=12000-9600, 10b=2400, b=240. ———————————————————————— 20a+10*240=9600, 20a+2400=9600. 20a=9600-2400, 20a=7200, a=360. (360+240=600 lei) 360*120/100=432 lei, (100+20%=120%=majorarea pretului cu 20%) 240*110/100=264 lei, verificatea 432+264=696.
