Any help with this for the correct answer 90 points

Answer:
Here, Length = y
Width = x
It is given that, y = 3x
1) Linear Equation for Perimeter, P = 2 (l + w)
84 = 2(3x + x)
84 = 2(4x)
84 = 8x
2) Linear equation for relation of Length & width would be:
y = 3x