1. **Stating the problem:** We have an incomplete frequency distribution table of marks and number of students. We need to find the missing frequencies. 2. **Given data:** | Marks | 0-10 | 10-20 | 20-30 | 30-40 | 40-50 | Total | |---------------|-------|--------|--------|--------|--------|-------| | No. of students | 4 | x | 10 | y | 10 | 50 | 3. **Formula and rule:** The sum of all frequencies must equal the total number of students. $$4 + x + 10 + y + 10 = 50$$ 4. **Simplify the equation:** $$4 + 10 + 10 + x + y = 50$$ $$24 + x + y = 50$$ 5. **Find the sum of missing frequencies:** $$x + y = 50 - 24 = 26$$ 6. **Conclusion:** The sum of the missing frequencies for the intervals 10-20 and 30-40 is 26. Without additional information, we cannot find the individual values of $x$ and $y$. If you have more data or conditions, please provide them to find exact values.