What you do to on side of an equation (=) you must do to the other to keep both sides equal.
r3-2+2=+2 (add 2 to both sides of the equation to simplify the left side)
which becomes
r3=2
r3/3 = 2/3 (divide both sides by 3) Note 3/3 =1 and 1 r is the same as r
which becomes
r=2/3 .