A rectangular piece of land, 400 meters wider, becomes a square, and the area increases by 56 hectares. How many square meters is the original rectangular area

56 ha = 560000 M2
Rectangle length = 560000 / 400 = 1600m
Rectangular area = 1600 × (1600-400) = 1920000 square meters

How many hours does it take for 3 tractors to plough 6.6 hectares in 2 hours and 1 tractor to plough 21.56 hectares?

Every tractor ploughs every hour
6.6 △ 3 △ 2 = 1.1 ha
One tractor needs 21.56 hectares of arable land
21.56 △ 1.1 = 19.6 hours