1. The problem asks to find the translation rule that maps triangle BCD to triangle B'C'D'. 2. The translation rule is generally written as $$(x, y) \mapsto (x + a, y + b)$$ where $a$ and $b$ are the horizontal and vertical shifts respectively. 3. Identify the coordinates of a vertex before and after translation. For example, vertex B moves from $B(-9, -9)$ to $B'(3, 3)$. 4. Calculate the horizontal shift $a$: $$a = 3 - (-9) = 3 + 9 = 12$$ 5. Calculate the vertical shift $b$: $$b = 3 - (-9) = 3 + 9 = 12$$ 6. Therefore, the translation rule is $$(x, y) \mapsto (x + 12, y + 12)$$ 7. This means every point of triangle BCD is moved 12 units right and 12 units up to get triangle B'C'D'.