Answer:
25
Explanation:
The angle at C is 90 degrees, and BCD is a right triangle, so we can applythe Pythagorean theorem here -- 60²+m²=65², so 65²-60²=m²=625. The possible values for m are 25 and -25, and since m can't be negative, 25 is our answer as 25 is the square root of 625