10. (3 points) Li Gang delivered honeycomb coal to Grandma Wang, a military family member. The first time, he delivered $\frac{3}{8}$ of the total, and the second time, he delivered 50 pieces. At this point, the amount delivered is exactly $\frac{5}{7}$ of the amount not yet delivered. There are still $\qquad$ pieces of honeycomb coal not delivered.