If you would like to know how many points did Nelson score, you can calculate this using the following steps:
Craig: 12 points
Nelson: n points = ?
Marla: twice as many points as Craig ... 2 * 12 points = 24 points
5 fewer points than Nelson ... n - 5
n - 5 = 24
n = 24 + 5
n = 29 points
The correct result would be 29 points.