Answer:
a=10
Explanation:
use a^2+b^2=c^2
(a+2)^2+(a-5)^2=(a+3)^2
a^2+4a+4+a^2-10a+25=a^2+6a+9
2a^2-6a+29=a^2+6a+9
a^2-12a=-20
a^2-12a+20=0
quadratic formula→(12+/-8)/2
a=10 or 2
2 is not an option because 2-5=-3 which isn't possible in this case.
so a=10