Solve 2r ≤ 3(2r - 7)
2r ≤ 3(2r - 7)2r ≤ 6r - 2121 ≤ 6r - 2r21 ≤ 4r21/4 ≤ rr\(\geq\) 21/4r \(\geq\) 5.25
