Let length of land be x.
Thus, perimeter of land = 50m + 50m + x + x = 100m + 2x
Cost of fencing land is Rs 18 per meter, so cost of fencing land will be
= (100 + 2x) * 18
= 1800 + 36x
The actual cost is Rs 4680, so we have:
4680 = 1800 + 36x
36x = 4680 - 1800
36x = 2880
x = 2880 / 36
x = 80
Thus, length of land is 80m.
Area of land
= length * width
= 80m * 50m
= 4000m^2
Cost of leveling plot
= Rs7.6 * 4000
= Rs 30400