$a)\left(7x-4y+5z\right)-\left[-\left(-z+10y\right)+\left(2y+5x\right)\right]-\left[-\left(-x-y-z\right)\right]=7x-4y+5z-\left[z-10y+2y+5x\right]-\left[x+y+z\right]=7x-4y+5z-\left[z-8y+5x\right]-x-y-z=7x-4y+5z-z+8y-5x-x-y-z=$

$=7x-5x-x-4y+8y-y+5z-z-z=x+3y+3z$

$b)-\left(-4a^2{b}^2+3a{b}^2-2a^{2}b\right)-\left[-\left(a^2{b}^2-2a^{2}b\right)+15a{b}^2\right]=4a^2{b}^2-3a{b}^2+2a^{2}b-\left[-a^2{b}^2+2a^{2}b+15a{b}^2\right]=$ $4a^2{b}^2-3a{b}^2+2a^{2}b+a^2{b}^2-2a^{2}b-15a{b}^2=$

$=4a^2{b}^2+a^2{b}^2-3a{b}^2-15a{b}^2+2a^{2}b-2a^{2}b=5a^2{b}^2-18a{b}^2$

$c)25x^{2}y-\left[5x{y}^2-\left(-10y{x}^2+7x^2{y}^2\right)-\left(3y^{2}x-11y^2{x}^2\right)\right]=25x^{2}y-\left[5x{y}^2+10y{x}^2-7x^2{y}^2-3y^{2}x+11y^2{x}^2\right]=25x^{2}y-\left[5x{y}^2+10x^{2}y-7x^2{y}^2-3x{y}^2+11x^2{y}^2\right]=$

$=25x^{2}y-\left[5x{y}^2-3x{y}^2+10x^2-7x^2{y}^2+11x^2{y}^2\right]=25x^{2}y-\left[2x{y}^2+10x^{2}y+4x^2{y}^2\right]=25x^{2}y-2x{y}^2-10x^{2}y-4x^2{y}^2=25x^{2}y-10x^{2}y-2x{y}^2-4x^2{y}^2=15x^{2}y-2x{y}^2-4x^2{y}^2$

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