Question 4
Bác Tư grows vegetables and beans on a fixed rectangular plot. This year he turns the rectangular vegetable patch into a square by extending one side by 3 m, as shown. The bean area decreases by 30 square metres. What was the vegetable area before the change? Show your reasoning. The upper diagram is before the change and the lower diagram is after it; “Rau” means vegetables and “Đậu” means beans.
