You need to remember the formula of area of rectangle such that:
A = length*width
Since the problem provides the value of area of `234 m^2` , the length of `(x+8)` and the width of `(x+3), ` you need to substitute these values in equation of area such that:
`234 = (x+8)(x+3)`
Opening the brackets yields:
`234 = x^2 + 3x + 8x + 24 => x^2 + 11x - 210 = 0`
You may use quadratic formula to find x such that:
`x_(1,2) = (-b+-sqrt(b^2-4ac))/(2a)`
You need to identify a,b,c such that:
`a=1 , b = 11 , c = -210`
`x_(1,2) = (-11+-sqrt(121+840))/2 => x_(1,2) = (-11+-sqrt961)/2`
`x_(1,2) = (-11+-31)/2 => x_1 = 10 , x_2 = -21`
Since the length and the width are `(x+8)` and (x+3), then only the value x = 10 is valid.
`x+8 = 10+8 = 18`
`x+3 = 10+3 = 13`
Hence, evaluating the length and the width of the given rectangle, under the given conditions, yields `x+8=18 m` and `x+3=13 m` .