Răspuns :
50×20+40+50 = 50·(20+1) +40 = 50·21 +40 = 1050+40 = 1090
50×20+40+50 = 1000 + 90 = 1090
50×20+40+50 = 50·(20+1+1) -10 = 50·22 -10 = 1100-10 = 1090
50×20+40+50 = 50·(20+1) +40 = 50·21 +40 = 1050+40 = 1090
50×20+40+50 = 1000 + 90 = 1090
50×20+40+50 = 50·(20+1+1) -10 = 50·22 -10 = 1100-10 = 1090