-12 + 2a = -6 (1+a)?
Answer is 0 = 6
A = W· L
10,000 = W ( W +30 ) = W² + 30 W
W² + 30 W - 10,000 = 0
W =

L = 86.12 + 30 = 116.12
Width of a plot is 86.12 m and lenght is 116.12 m.
Check : A = 116.12 · 86.12 ≈ 10,000
KX = x+4 so solve for k.
Divide both sides of the equation by x and you get K=4.
Plug it in, and you get (4)(7)=28
Your answer is 28.