AB + DO - OB + OC + CD = AB + (DO - OB) + OC + CDAB + (D + O) - OB + OC + CDAB + D + O - OB + OC + CDAB + O + OB + OC + CDAB + OC + CD + OBAB + OC + CD + BOAB + OC + CD + OB
Ответ: AB + OC + CD + OB.
AB + DO - OB + OC + CD = AB + (DO - OB) + OC + CD
AB + (D + O) - OB + OC + CD
AB + D + O - OB + OC + CD
AB + O + OB + OC + CD
AB + OC + CD + OB
AB + OC + CD + BO
AB + OC + CD + OB
Ответ: AB + OC + CD + OB.