1) 2а-3b-(4a+7b+c+3) 2) 2xy-y^2+(y^2-+xy) 3) (-2x^2+x+-x++2x+8) 4) (3a^2-a+2)+(3a^2+3a--1) 5) (1-x+4x^2-8x^3)+(2x^3+x^2-+x--8x^2) 6) (0.5a-0.6b+5..5a+0.4b)+(1.3b-4.5) 7) (x^2)^4*(x^4)^3 8) (a^2*a^3)^4 9) 10) 11)

1) 2а-3b-(4a+7b+c+3) = 2a - 3b - 4a - 7b - c - 3 = -2a - 10b - c - 32) 2xy-y^2+(y^2-xy)-(x^2+xy) = 2xy - y^2 + y^2 - xy - x^2 - xy = -x^2
3) (-2x^2+x+1)-(x^2-x+7)-(4x^2+2x+8) = -2x^2 + x + 1 - x^2 + x - 7 - 4x^2 - 2x - 8 = -7x^2 -14 = -7(x^2 + 2)
4) (3a^2-a+2)+(3a^2+3a-1)-(a^2-1) = 3a^2 - a + 2 + 3a^2 + 3a - 1 - a^2 + 1 = 5a^2 + 2a + 2
 5) (1-x+4x^2-8x^3)+(2x^3+x^2-+x-3)-(5x^3-8x^2) = 1 - x + 4x^2 - 8x^3 + 2x^3 + x^2 + x - 3 - 5x^3 + 8x^2 = -11x^3 + 14x^2 - 2
6) (0.5a-0.6b+5.5)-(-0.5a+0.4b)+(1.3b-4.5) = 0.5a - 0.6b + 5.5 + 0.5a - 0.4b + 1.3b - 4.5 = a + 0.3b + 1
7) (x^2)^4*(x^4)^3 = x^8 * x^12 = x^(8 + 12) = x^20
8) (a^2*a^3)^4  = a^4(2 + 3) = a^(4*5) = a^20