Hello!
You can use the Pythagorean Theorem

c is the hypotenuse which is the side across the right angle
a and b are the other sides
Put in the values you know

Square the numbers

Subtract 25 from both sides

Take the square root of both sides
a = 10.9
The answer is D) 10.9 centimeters
Hope this helps!
Having the angle in radians and the diameter of the circle we can easily calculate the length using the following expression
Length = angle(radians)*diameter/2
With this expression we can easily deduce the perimeter of a circle (length of the full arc)
Length = Perimeter = 2*pi*r
There is only one operation involved in this process
Slope = -3/2
..........................
The answer is 24" hope this helps.