8 brownies divided by 5 people=8/5=1 3/5
A triangle should have 3 points and 3 sides. Let say that the point is ABC. Then the sides would be AB, AC and BC.
There are 3 strings with a different length that can be put into the sides. Assuming the string can be used once, then the possible way would be:
3!/(1+3-3)!= 3!/1!= 3*2*1= 6 ways
(x - 8)² = 144
Take square root of both sides
(x - 8) = √144
x - 8 = 12
x = 12 + 8
x = 20
Original lawn is = 20 feet * 20 feet square
The given equation is: 
To find the line perpendicular to it, we interchange coefficients and switch the signs of one coefficient.
The equation to a line perpendicular to it is:
$ 2y-x=c$
where, $c$ is some constant we have determine using the condition given.
It passes through $(2,-1)$
Put the point in our equation:
$2(-1)-(2)=c$
$c=-2-2$
$c=-4$
The final equation is:
$\boxed{ 2y-x=-4}$