1) 3x + 5 = 20 → 3x = 15 → x = 5
2) 2² + 3² = 4 + 9 = 13
3) √64 + 7 = 8 + 7 = 15
4) (18 ÷ 3) × 5 = 6 × 5 = 30
5) 6! = 6×5×4×3×2×1 = 720
6) 4x - 7 = 9 → 4x = 16 → x = 4
7) 15 + 2 × 6 = 15 + 12 = 27
8) 3³ - 5 = 27 - 5 = 22
9) √81 + √16 = 9 + 4 = 13
10) (5 + 3) × (2 + 1) = 8 × 3 = 24