5 of 18 * 7 + 8 of 38 * 21-2 of 7 * 18 + 1 of 21 * 38

5 of 18 * 7 + 8 of 38 * 21-2 of 7 * 18 + 1 of 21 * 38

The first minus the third = 3 / 7 * 18, the second plus the fourth = 3 / 7 * 38
Together = 3 / 7 (18 + 38) = 24