1. 75x - 18x -9y -3y -4x = 53x - 12y
2. 45a + 41a + 39b - 8b + 52a = 138a + 31b
3. 72u - 26v - 18u - 56u - 71v = -2u - 82v
4. 58a + 83b - 43a - 37b - 67b + 100a = 115a - 21b

5. 1/4u + 1/2v + 1/8w + 16/5u - 2/5v - 2/4u - 31/6w
   
=> 5/20u + 5/10v + 3/24w + 64/20u - 5/10v - 10/20u - 124/24w

   59/20u -121/24w  =  2 19/20u - 5 1/24w

6. 2a(3x + 4y) = 6ax + 8ay
7. -6(7x - 9y - 3 ) = -42x +54y + 18
8. 3a(7x - 5 ) +2a(4 - 3x) = 21ax - 15a + 8a - 6ax = 15ax - 7a
9. 7x² + 3x(2x - 5y) = 7x² + 6x² - 3xy = 13x² + 3xy
10. 8r ( 2x + 3t)+(7s-3t)*4r = 16rx + 24rt +28sr - 12rt = 16rx +12rt + 28rs
11. (-x-2y)(-x+y) = x²-xy +2yx -2y² = x² + xy - 2y²
12. (a - b)(a² - ab + b²) = a³ - a²b + ab² -a²b +ab² -b³ = a³ -2a²b +2ab² - b³
13. (2a - 10)(-b-13) = -2ab - 26a + 10b + 26
14. (3x+2y)(9x -2y -3z) = 27x³ -6xy -9xz + 18xy -4y² -6zy = 27x² +12xy -4y² -6zy

15. (x+y)(x-2y)-(16x + 20y)(5x+9) = x² -2xy +xy -2y² - 80x² +  144x + 100xy + 180y

=> -79x² -144x +99xy + 180y - 2y²

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