The process is:
C = 2nr
2nr = c
r (2n) = c

That's the answer☝️☝️☝️☝️
or maybe this one
r = 2n + c
sorry, I'm unsure, it has been too long since I studied that...
Answer:
Step-by-step explanation:
t=45
value=3
Given
0.24 × (number of 6th grade students) = 30
Find
(number of 6th grade students
Solution
Divide by 0.24.
... (number of 6th grade students) = 30/0.24 = 125
Answer:392.5
Step-by-step explanation:
50/2=25
25*25=625
625*3.14=1962.5
1962.5/5=392.5