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
Since the second equation gives a value for a, we can substitute it into the other equation to find a value for B.
Let's substitute b-2 into the first equation wherever there is an a.
a - 3b = 4
(b-2) - 3b = 4
b - 2 - 3b = 4
-2 - 2b = 4
-2b = 6
b = -3
Now let's find a by substituting -3 into either of the equations to find the value of a.
a = b - 2
a = -3 - 2
a = -5
So your solution set is (-5, -3)
18.84
Since the formula of circumference is C = 2 pi r or C = pi times diameter, you can conclude that the circumference is 18.84.
Assuming that pi is 3.14 in this case rather than the full pi or just in terms of pi.
Hope this helps!