Answer: 11 deer and 13 birds. Explanation: Let the number of deer be D (4 legs), and birds be B (2 legs). Each animal has one head, so we form the system of equations: ① D + B = 24 (heads), ② 4D + 2B = 74 (legs). From ①: B = 24 – D. Substitute into ②: 4D + 2(24 – D) = 74 → 4D + 48 – 2D = 74 → 2D = 26 → D = 13. Then B = 11. But this leads to 13 deer and 11 birds → 4×13 + 2×11 = 52 + 22 = 74 legs, D + B = 24 heads ✅. So correct numbers are 13 deer and 11 birds, not 11 deer and 13 birds.