Answer:
k = 4 units
Step-by-step explanation:
Using Pythagoras' identity on the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
k² + 7.5² = 8.5²
k² + 56.25 = 72.25 ( subtract 56.25 from both sides )
k² = 16 ( take the square root of both sides )
k = = 4