Question 330733
Let three sides of the triangle be
l for long
m for middle
s for short

Then,
l + m + s = 84 ...(a)
s = m - 9 ...(b)
l = m + 6 ...(c)

Substituting equation (b) and (c) in (a),

m - 9 + m + m + 6 = 84

3m = 87
Therefore, m = 87/3 = 29

From (b), s = 29 - 9 = 20
From (c), l = 29 + 6 = 35