In the second one I'm pretty sure you just measure the length of the points.
Step-by-step explanation:
4x2 - 25b2
We can solve it by the squares so
(2x - 5b) (2x + 5b)
2) x2 - 81
The same case is here so
(x - 9) (x + 9)
The area, assuming is a rectangular floor, is their product.
so simply convert the mixed to improper and get their product.