4x = 5x -12
4x - 5x = 5x - 5x - 12
-x = -12
x = 12
The correct answer is A) the area is 24 ft^2 and the perimeter is 20 feet
To find the perimeter:
2(6)+2(4)=12+8=20
2(L)+2(W)=perimeter
L=length and W=width
To find the area:
L*W=A
6ft*4ft=24ft^2
0.53
Step-by-step explanation:
First, Delete these brackets on the right side:

Left side and right side are equal, so each parameters have to be equal. Next to "x^2" you've got parameters "6" and "3n". So:
3n=6 /:3
n=3Free terms are "6" and "3m", so:
3m=6 /:3
m=2Next to "x" you've got "b" and "9+nm" . We know, that m=2 and n=3 so:
b= 9+nm
b=9+2*3=9+6
So
b=15