i need help with this i cant cuaet understand this Find the radius given the diameter

Given the diameter of a circle, we can find its radius by dividing the diameter by 2, like this:
[tex]r=\frac{d}{2}[/tex]Where r is the radius and d is the diameter of the circle, by replacing 30 for d, we get:
[tex]r=\frac{30}{2}=15[/tex]Then, the radius of this circle equals 15 m