16m²
Step-by-step explanation:
First, get the area of rectangular vegetable box planted with pechay.
A = l × w , where l = 5m, w = 4m
A = 5m × 4m = 20 m²
Next, get the small square box of onions inside the rectangular box.
A = a × a , where a = 2m
A = 2m x 2m = 4 m²
Then, subtract the 20m² – 4m² = 16m²
Thus, the total area of the box planted with pechay is 16m².
