Answer:
[tex]4.2\ \text{cm}[/tex]
Step-by-step explanation:
d = Diameter of wheel
The difference between the circumference and diameter of a wheel is 18 cm.
[tex]2\pi r-d=18\\\Rightarrow \pi d-d=18\\\Rightarrow d(\pi-1)=18\\\Rightarrow d=\dfrac{18}{\pi -1}\\\Rightarrow d=\dfrac{18}{3.14-1}\\\Rightarrow d=8.41\ \text{cm}[/tex]
The diameter of the wheel is 8.41 cm so the radius will be [tex]\dfrac{8.41}{2}=4.205\approx 4.2\ \text{cm}[/tex].
