Final answer:
To find the value of C, simply add r to 3.
Step-by-step explanation:
To find the value of C, we need to isolate C on one side of the equation. In the given equation, C - r = 3, we want to get rid of the -r term. To do this, we can add r to both sides of the equation:
C - r + r = 3 + r
Simplifying, we get:
C = r + 3
So, the value of C is r + 3.