Divide the amount saved by the original price then multiply by 100 to get the percent:
6/40 = 0.15
0.15 x 100 = 15%
The area would be 144cm^2.
In order to find the area, we need to know the length of the rectangle. We can find that using the perimeter formula.
2l + 2w = P
2l + 2(36) = 80
2l + 72 = 80
2l = 8
l = 4
So now that we know the length is 4, we can find the area using that formula.
A = lw
A = (4)(36)
A = 144
0.003 is 1/10 of 0.03.
Just multiply the 0.003 by 10 and you'll get the result. The easiest way to multiply such numbers is to move the dot one position to the right (it would be 2 positions if multiplying by 100, 3 by 1000 etc.). You can do the same with dividing, just remember to move to the left then.
X = -126/5 or -25.2 or -25 1/5