consider the numbers are x,2x,3x,4x,5x
Given;
(x+2x+3x+4x+5x)/5 = 11
15x = 55
x= 55/15 = 11/3
The numbers are
11/3, 22/3, 11, 44/3, 55/3
15, because 3 goes into 9, 3 times and, 4 goes into 12, 3 times therefore x has to follow this rule because these 2 triangles are similar and because it already gives you 5 just take 5*3=15 there is your answer enjoy!=)
X² n = 1,2,3,4,5
1² = 1
2²= 4
3²= 9