Perimeter = 74cm
Let x be the shortest side
Let y be the middle side
Let z be the longest side
1) x + y + z = 74
2) z = x + y - 10
3) 2x = z - 2
From equation 1, we get
x + y = 74 - z
Substitute into equation 2.
z = (74 - z) - 10
z = 64 - z
2z = 64
z = 32
Substitute z = 32 into equation 3.
2x = 32 - 2
2x = 30
x = 15
Substitute x = 15 & z = 32 into equation 1.
15 + y + 32 = 74
y = 74 - 32 - 15
y = 27