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.
