To solve this we can use Pythagorean's theorem for right triangles. The formula describes the longest side of a right triangle ( a triangle with a 90degree ). The side opposite to this angle equals the square root of the sum of the squares of the other two shorter sides. Given this equation, we have the length of the ladder as the longest side (hypotenuse) which is opposite the angle between the plane and the wall, given the height it makes with the wall 8 feet and distance of the other end of the ladder at 6m away we have below
Length of ladder = sqrt ((6 m)^2+(2.4384m)^2)
Note that 8 feet was converted to meter = 2.4384
Length of ladder is = sqrt (36 + 5.94579456) = 6.5 meters approximately