You can
put this solution on YOUR website!you are over thinking this
"the height of the sail is x+3 meters" __ 5+3=8
area of a triangle is 1/2 * base * height
56 = 1/2 * b * 8
b = 14
BUT--the question may be asking for the general solution
x^2+5x+6 = 1/2 * b * x+3
dividing by x+3 __ x+2 = 1/2 * b
b = 2x+4