Also, I think that Brainly is an awesome app, but there's an app which is doing great work for me in maths, named Gauthmath. I will suggest it. Video concepts and answers from real tutors.
You could set up a proportion to figure out the anwer. 15 hurdles/60%=X hurdles/100%. Cross multiply, 1500=60x. Divide by 60, 25=X=total amount of hurdles. Hope this helps!