Simplify:

(i) 7x – 9y + 3 – 3x – 5y + 8;

(ii) 3x² + 5xy – 4y² + x² – 8xy – 5y².

Separate the monomials, binomials and trinomials from the following:

7xyz, 9 – 4y, 4y² – xz, x – 2y + 3z, 7x + z², 8xy, x²y², 4 + 5y – 6z.

Classify into like terms:

4x², x, –8x³, xy, 6x³, 4y, –74x³, 8xy, 7xyz, 3x².

Add:

(i) 5a + 3b, a – 2b and 3a + 5b;

(ii) x³ – x²y + 5xy² + y, –x³ – 9xy² + y, and 3x²y + 9xy².

Subtract:

(i) –2xy + 3xy² from 8xy;

(ii) a – b – 2c from 4a + 6b – 2c.