XXX + XXV = ___
LL
XX
DD
LV
XXX = 10 + 10 + 10 = 30 XXV = 10 + 10 + 5 = 25 Thus, XXX + XXV = 30 + 25 = 55 But, 55 = 50 + 5 = L + V = LV Thus, XXX + XXV = LV