In this 4x4 grid, the sum of each row is 44: (15+3+7+19=44), (8+11+5+20=44? No). Looking at columns: 15+8+5+14=42, 3+11+2+7=23. The logic is the sum of the first three numbers in a row equals the fourth? 15+3+7=25 (no). 14+7+14=35. If the sum is 56? 35+21=56. 21 is the intended answer.