a: /_______/
b: /_______/ +2 a + b + c = 21
c /_______/ +2 +2
a+ b + c + d +e = 81
d: /_______/
e: /_______/_______/ d + e = 60
a + b + c = 81 - 60 = 21
21 - (2 + 2 + 2 ) = 21 - 6 = 15
15 : 3 = 5 (un segment)
a = 5
b = 5 +2 = 7
c = 5 + 4 = 9
d : e = 2 ⇒ e = 2d
d + e = 60
60 : 3 = 20 (un segment)
d = 20
e = 20 x 2 = 40
e - a = 40 - 5 = 35