Add :

x³ - x²y + 5xy² + y³, -x³ - 9xy² + y³, 3x²y + 9xy²

Find the total savings of a boy who saves ₹ (4x - 6y), ₹ (6x + 2y), ₹ (4y - x) and ₹ (y - 2x) in four consecutive weeks.

Subtract:

- 2x²y + 3xy² from 8x²y

Subtract:

3a - 5b + c + 2d from 7a - 3b + c - 2d