Answer:
-ad-r=C
-------- Sorry thats the best I could do for a fraction symbol
3-b
Explanation:
In order to solve for C we need to get it C on one side of the equation all by itself. To start we can subtract R from both sides and subtract bc from both sides to get both C's on one side. That gets us to
-ad-r=3c-bc
Since the side with C has a common factor, C between 3c and bc we can pull that out, and we get
-ad-r=c(3-b)
and then we just divide 3-b on both sides to get C completely by itself
-ad-r=C
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3-b
I hope this helps and please don't hesitate to ask if there is anything still unclear!