If your trying to find x, distribute 2(x+6), which is by multiplying 2 times x, which is 2x and 2 times 6, which is 12. So your left off with 4x+2=2x+12. In order to find x, we have to move the 2 to the right, which will give us 2x+10 and then move 2x to the left to give us 2x=10. Divide both sides by 2, and x= 5.
N= numbers
x= x-ray
4 unknown number equal a unknown amount of x-rays mutiplyed but 5-unknow number.
x can stand for anything and so can n
Let width of rectangle be "x"
L= 3x W=x
if width is diminished by 1 that means new width = (x-1)
similarly the new length would be (3x+3)
hence (x-1)*(3x+3)=72
(3x^2)-3=72
3x^2=75
x^2=25
x= +/- 5
reject -5 as you cant have negative length
hence x=5
so original dimensions of rectangle is
L= 15m W=5m