{3a-6a+5b+7c}+2a-3c-3a+4b-2c

=-3a+6a-5b-7c+2a-3c-3a+4b-2c=2a-b-12c.

20. 7a2-{3a2 - 2b2+3c2+4a2 – 5c2} + b2 - c2 - 3b2- c2 - 9b2

=7a2-3a2+262 - 3c2-4a2+5c2 + b2 - c2 - 362 - c2 - 9b2= — 962.

21. 3x2-[4x+5x2 - 2x2 - 3x]=3x2 - 4x - 5x2+2x2+3x= −x.

22. 4x-[3x - {2x-2x+5+4}]=4x-[3x-2x+2x-5-4]

=4x-3x+2x-2x+5+4=x+9.

=5x2+3x-13.

23. 12x2-[7x2 - 5x+4x-2x+1+12]=12x2 - 7x2+5x-4x+2x-1-12

=3a-12a-5b+3c-4b-2a+3b+2c=-11a-6b+5c.

25. 4x+[7y-2z −5+x] - [4x+3y-2z+7]

=4x+7y−2z−5+x-4x-3y+2z-7=x+4y-12.

26. 2x3- 4x2 - [3x – {5x – 2x2 - 7}] − 2x3 + 6x2 – 2x
=2x3- 4x2 - [3x-5x+2x2+7]-2x3+6x2 - 2x
=2x3-4x2-3x+5x-2x2-7-2x3+6x2-2x= -7.

27. 4a-2b-[3a-2b+2a-2c-4a+b+c]

=4a-2b-3a+2b-2a+2c+4a-b-c=3a-b+c.

28. 7x2-[2x - {2x2-3x+4} -3x]+5x+3x+7

29.

=7x2-[2x-2x2+3x-4-3x]+5x+3x+7

=7x2-2x+2x2 - 3x+4+3x+5x+3x+7=9x2+6x+11.

ab

− 4a2+b2+2a2 – b2+3c2+4ab+4a2 - {3b2 - 2c2+bc}
=-4a2+b2+2a2-b2+3c2+4ab+4a2-3b2+2c2 - bc - ab

=2a2+3ab-362-bc+5c2.

30. 5x-[x2- {2y2 − xy +2z2}+3y2]+2x2+5xy − y2+z2

=5x2 - [x2 - 2y2+xy − 2z2+3y2]+2x2+5xy-y2+z2
=5x2 — x2+2y2 — xy +2z2 — 3y2+2x2+5xy − y2+22
=6x2+4xy - 2y2+3z2,

31. 4a- (3a-(2a - 6a - 1)} - (4a - 5a+2)

=4a- {3a-2a+6a+1}-4a+5a - 2

=4a-3a+2a - 6a-1-4a+5a-2=-2a-3.

32. 7a2- {5a2 - 2a+2a2 - 7a+5}+3a2 - 4a+12

=7a2-5a2+2a-2a2+7a-5+3a2-4a+12=3a2+5a+7.

=5a2-2a+7-3a2+2a+5a-6-2a2+7=5a+8.

34. 2x-[3y-2z+ {4x - (5y-3x+2x)}+5z]

35.

=2x-[3y-2z+4x-5y+3x-2z+5z]

=2x-3y+2z-4x+5y − 3x+2z – 5z= − 5x+2y – z.

a-[2b+ {3c - (3a-a+b−c)} +2b–3c]
=a-[2b+3c-3a+a−b+c+2b −3c]

=α- -2b-3c+3a-a+b-c-2b+3c=3a-3b - c.

36. 3x2-[4x-5- {2x2-7x-2-4x2+2x-7}]

=3x2-[4x-5-2x2+7x+2+4x2 – 2x+7]
=3x2-4x+5+2x2-7x-2-4x2+2x-7= x2 - 9x-4.

37. 5a-7b-4c-[6a-3b-2c+4c-{2a-b+2a - c}]

=5a-7b-4c-[6a-3b-2c+4c-2a+b-2a+c]

=5a-7b-4c-6a+3b+2c-4c+2a-b+2a-c-3a-5b-7c.

38. 8x2-5xy+6y2 - [2x2 - {3xy - y2+3x2 - 2xy - 5y2}]

39.

=8x2-5xy+6y2 – 2x2+3xy-y2+3x2 - 2xy - 5y2 = 9x2 - 4xy.

- x2 - 2ax+3a2+ [a2 − x2 — {2ax - a2+7ax+5x2} – 2ax]

− − x2 – 2ax+3a2+a2 − x2 - 2ax+a2 - 7ax - 5x2 - 2ax

=-7x2-13ax+5a2.

40. 11a3-2a2+3a - [7a-2+9a3+12a2 - 11a+5− a3]
=11a3-2a2+3a-7a+2-9a3 - 12a2+11a−5+a3
=3a3-14a2+7a-3.

41. 11x-7+8x-6+7x-14=26x-27.

42.

5x2-3-8x+1-8x2-10x+6= −3x2 – 18x+4.`

43. 4a-22a-11b+33c+21a-7b=3a-18b+33c=3 (a -6b+11c).

44. 6a2-12a+30-2a3 - 2a2-2-a3+a2-2a+3=-3a3 +5a2 - 14a+31. 45. 4x2-12x+8-6x2-12 – 35x2+15x+60=-37x2+3x+56.

46. 5x2-3x+x2 - 4+8x2 - 2x+10+15=14x2 − 5x+21.

47. 2a2-3a2-a+2a2 - 10a +12-3a2+6a+3=-2a2 - 5a+15.

48. 6x2+4xy-4xz+3xy - 3xz+3y2 – 3x2+6y2=3x2+7xy − 7xz+9y2.

49. 4a2-4ab-3a2+6ab+3b2+2a2 - 2ab=3a2+3b2=3 (a2+b2).

50. a3-2a2+10a3 - 30a2 - 5 (a3 — a2+2a)

=a3-2a2+10a3 - 30a2 - 5a3+5a2 - 10a
=6a3 - 27a2 - 10a=a (6a2 - 27a-10).

51. a2+ab-ac - 3ab+3b2+3bc+2ac+2bc+4c2

=a2-2ab+ac + 3b2+5bc+4c".

52. 3x2+2xy - xz - 3xy - 3y2 – 12yz+12xz - 6yz - 6z2

=3x2- xy +11xz-3y2 - 18yz - 6z2.

53. 7x2+7xy+7y2 – 12xy +24xz+3xy+6yz=7x2 - 2xy +7y2+24xz+6yz.

54. 2(x2+3x-3yz) - 5xy+10y+7 (y2-y2+yz)

=2x2+6x2 - 6yz - 5xy+10y2+7yz=8x2 - 5xy + 10y2+yz.

55. 3a2-[2a2-2a2+2a-2+2]

=3a2-2a2+2a2-2a+2-2=3a2 - 2a=a (3a − 2).

56. 3 [4x-5-6x+8+5 {2x-3-2x+7x-35}]

=3[4x-5-6x+8+10x-15-10x+35x-175]
=3[33x-187]=33 (3x-17).

57. 3a2-362- [2a2 - 2b2 - 2ab - 2b2+2ab]

=3a2-362-2a2+2b2+2ab+2b2-2ab=a2+b2.

58. x − [2x−x+6x+3y-6x-3y]=x-2x+x-6x-3y+6x+3y=0. 59. 7a4-7a2+14a+2a3-2a2+8a-3a3+3a2+3a4-6a2+3a3

60.

- 4x3 + 4x2y – 4x2z+3x2y - 3xy2+3xyz – 2x2y+6xy2 – 6y3

43. 15x-12x+2x=19+32 − 51; 44. 21x+15x+11x=47+26+14+7; 47x=94; .. x=2.

45.

5=0; .. =0.

42x-11x+13x=121+23 - 100;

44x=44; .. x=1.