Let x = no of hectares in the beginning
Now, 3/7 x → sold
x - 3/7 x = 15 3/4
Solving for x using linear equation in one variable:
28(x -3/7x) = 28(15 3/4)
28x - 12x = 28 (63/4) → converting mixed fraction to improper fraction
28x - 12x = 441
16x = 441
x = 441/16
x = 27 9/16 → converting improper fraction to mixed fraction