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...
There are free tutor on my website just got to freetutor.com
the number line scale already has 0 and 2 so inbetween them 0 and 2
Put a 1 then
after 2 go 3,4,5.
Behind the 0 are negatives so 0 -1 -2 -3 -4...
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The oppisite of 2 is -2! Becaus you have a positive 2 and the oposite would be negative.</h2>