2. In a small fishing game, each time you catch a small fish or a small turtle. If you catch a small fish, you get 5 points, and if you catch a small turtle, you lose 2 points. Luo Xiahei played 17 times, and his score increased from 100 points to 157 points. Out of these 17 times, he caught a small fish $\qquad$ times.
$13$