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