typo in 2.3.6 ex 4

[rzeta0]

The prose says

Let x and y be real numbers and suppose that x=2 or y=-2. Show that x^2 + 2x = 2y + 4.

But the code says

example {x y : ℝ} (h : x = 2 ∨ y = -2) : x * y + 2 * x = 2 * y + 4 := by
  sorry

The inconsistency is xx vs xy.