D
just subtract 14 from 26
Let the width be x, the length is then 3x-10
Area of a rectangle is length times width: x(3x-10)=77 => 3x^2-10x-77=0
Factor this quadratic equation: (x-7)(3x+11)=0 =.x=7 or x=-11/3
width cannot be negative, so the only answer is x=7
width is 7m, length is 11m
I presume you're trying to find n, so first remove the 7 from each side.
8n + 7 -7 = 31-7
=> 8n = 24
Then divide both sides by 8, as you want only n
8n/8 = 24/8
n = 3
