Do you know what K=2r-s is

Our goal is to get r all by itself on one side of the equals sign. To do this, we'll first add s to both sides

k=2r-s

+s + s

k+s=2r

Now, to get r alone, we need to get rid of the 2. Since 2 is multiplied by r, we need to divide it from both sides to get r alone.

k+s=2r

/2 / 2

(k+s) / 2=r

Since there are no numbers, that's the final answer.