Answer:
C
Step-by-step explanation:
Use the Pythagorean Theorem.
[tex]a^2+b^2=c^2 \\ \\ 100^2+b^2=125^2 \\ \\ 10000+b^2=15625 \\ \\ b^2=5625 \\ \\ b=\sqrt{5625} \\ \\ b=75[/tex]
