import Mathlib

set_option maxHeartbeats 0

open BigOperators Real Nat Topology Rat

theorem amc12b_2021_p4
  (m a : ℕ)
  (h₀ : 0 < m ∧ 0 < a)
  (h₁ : ↑m / ↑a = (3:ℝ) / 4) :
  (84 * ↑m + 70 * ↑a) / (↑m + ↑a) = (76:ℝ) := by sorry