Explanation:
step 1. This is a right triangle where a^2 + b^2 = c^2 (c is the hypotenuse).
step 2. a^2 + 6^2 = 8^2.
step 3. a^2 = 64 - 36.
step 4. a^2 = 28.
step 5. a (the ladder height along the wall) = sqrt (28) where sqrt is the square root.
step 6. sqrt(28) = 2(sqrt(7)).