.
Since the average is 100, the sum of the 5 numbers is 5*100 = 500.
The largest number is 120; hence, the second, third and fourth of the integers (by their magnitude) are not greater than 119, 118 and 117.
Thus
500 = 120 +
+
+
+
,
+
+
+
= 500 - 120 = 380,
119 + 118 + 117 +
>= 380,
>= 380 - 119 - 118 - 117 = 26.
Answer.
>= 26.
Solved.