theorem lean_workbook_plus_52558 : ∀ a b c : ℝ, 2 * a / (21 * a + 75 * b) + 2 * b / (21 * b + 75 * c) + 2 * c / (21 * c + 75 * a) + 1 / 7 + 1 / 10 * Real.sqrt ((a * b + a * c + b * c) / (a ^ 2 + b ^ 2 + c ^ 2)) ≤ 5 * Real.sqrt (a ^ 2 + 3 * a * b) / (21 * a + 75 * b) + 5 * Real.sqrt (b ^ 2 + 3 * b * c) / (21 * b + 75 * c) + 5 * Real.sqrt (3 * a * c + c ^ 2) / (21 * c + 75 * a) := by sorry