i) 3m + 12m -5m =(3+12-5)m
= (15 – 5) m
= 10m
ii) 25yz – 8yz – 6yz = (25 – 8 – 6) yz
= (25 – 14) yz
= 11 yz
iii) 10m2 – 9m + 7m – 3m2 – 5m – 8
= (10m2 – 3m2) + (-9m + 7m – 5m) – 8
= (10 – 3)m2 + (-9 + 7 – 5) m – 8
= 7m2 + (-7m) – 8
= 7m2 – 7m – 8
iv) 9x2 – 6 + 4x + 11- 6x2 – 2x + 3x2 – 2
= (9x2-6x2 + 3x2) + (4x-2x) + (-6 + 11 -2)
= (9 – 6 + 3) x2 + (4 – 2) x + (11 – 8)
= (12 – 6) x2 + 2x + 3
= 6x2 + 2x + 3
v) 3a2 + 4a2b – 7a2 – b2 – ab
= (3a2 + 7a2) – 4a2b – b2 – ab
= 10a2 – b2 – 4a2b – ab
vi) 5x2 + 10 + 6x + 4 + 5x + 3X2 + 8
= (5x2 + 3x2) + (6x + 5x) + (10 + 4 + 8)
= 8x2 + 1 lx + 22