Answer:
25

Explanation:
Looks like a quarter of a circle so you'd probably want to use the circle formula,
, but at the end divide by 4 because its only one quarter of it.
The radius is 10, not 5 since the section is already cut out.
so we go 10^2 = 100
100*

100
then divided by 4

and you can multiply those together if ya want but that's the most exact answer