Add: $121x+456x+81x+65x$

Add & Subtract: $15x^2+61x^2+7x^3-53x^3-2x^4+412x^4-321x^4$

Add & Subtract: $6x^3+5x^2-541x-400x+35-15$

Add & Subtract: $34x^2y+35x^2y-34xy^2+35xy^2$

Add & Subtract: $-17x^4-5x^3+5x^3-345x+23x^2-45x^4+54x$

Add & Subtract: $-56x^2y^2-72x^2y^2+37x^2y-567xy^2+65x^2-32y^2+x^3y^3-32x^2$

Subtract:$1000x-112x-346x-543x$

Subtract: $2000x^3-2001x^3+5432x^2-5431x^2-x-1$

Add & Subtract: $71x^3-54x^5+67x^3-412-31+71x-54x^5+32x$

Add: $10x^3+57x^3+32x^2+7x^2+100x+512$