The answer is: R = P + C
Steps:
First, move r to the left side of the equation and change its sign.
-r + p = - c
Then, move p to the right side and change its sign.
-r = -c - p
Multiply both sides of the equation by -1. This will change the variables back to positives, because any expression multiplied by -1 equals its opposite.
-1(-r) = -1(-c) -1(-p) =
r = c + p (don’t forget to change the sign)
So, your final solution is: r = c + p or r = p + c