7π/2 < 12 < 4π ⇒ 12 ∈ ④
-π < -3π/4 < -π/2 ⇒ -3π/4 ∈ ②
π/2 < 2.5 < π ⇒ 2.5 ∈ ②
5X2- 4X2 = 3 - 9/6+ 9/5
X2 = 3.3
X = 1.82
X = -1.82