The Pythagorean Theorum formula is a^2+b^2=c^2.
The hypotenuse equals c. Let's say that the 35-foot leg is b. That makes our formula c^2-b^2=a^2.
C Squared=4,900
B Squared=1,225
C Squared-B Squared=3,675
If we square root 3,675, that gives us our final answer, 60.6. Let's round it to 61.
The answer would now be B.
I hope I helped you!