Solve:

(a) 6x + (9x − 2x)

(b) 11y + 2y + 3x

(c) 11z + 3z + z

(d) 8ab + (−3ab)

(e) 3x − 4x + 7x

(f) 35b − (16b + 9b)

(g) (9a − 3a) + 4a

(a) 6x + (9x − 2x) = 6x + 7x = 13x.

(b) 11y + 2y + 3x = 13y + 3x = 13y + 3x.

(c) 11z + 3z + z = (11 + 3 + 1)z = 15z.

(d) 8ab + (−3ab) = (8 − 3)ab = 5ab.

(e) 3x − 4x + 7x = (3 − 4 + 7)x = 6x.

(f) 35b − (16b + 9b) = 35b − 25b = 10b.

(g) (9a − 3a) + 4a = 6a + 4a = 10a.