$a\text{)}W\left(x\right)-P\left(x\right)=\frac{3}{4}{x}^7-\frac{3}{8}{x}^6+\frac{1}{8}{x}^5+8-\left(0,75x^7+\frac{5}{8}{x}^6+0,125x^5+2\right)=$  

$=\frac{3}{4}{x}^7-\frac{3}{8}{x}^6+\frac{1}{8}{x}^5+8-0,75x^7-\frac{5}{8}{x}^6-0,125x^5-2=$  

$=\left(\frac{3}{4}-0,75\right)x^7+\left(-\frac{3}{8}-\frac{5}{8}\right)x^6+\left(\frac{1}{8}-0,125\right)x^5+\left(8-2\right)=$  

$=-x^6+6$  

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$b\text{)}W\left(x\right)-P\left(x\right)=4x^3-12x^2+0,6x+0,4-\left(-4x^3-12x^2+0,5x+0,4\right)=$  

$=4x^3-12x^2+0,6x+0,4+4x^3+12x^2-0,5x-0,4=$  

$=\left(4+4\right)x^3+\left(-12+12\right)x^2+\left(0,6-0,5\right)x+\left(0,4-0,4\right)=$  

$=8x^3+0,1x$  

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$c\text{)}W\left(x\right)-P\left(x\right)=3x^6-\sqrt{2}{x}^5+2\sqrt{2}{x}^3+8x-\left(5x^6-2\sqrt{2}{x}^5+4x-1\right)=$  

$=3x^6-\sqrt{2}{x}^5+2\sqrt{2}{x}^3+8x-5x^6+2\sqrt{2}{x}^5-4x+1=$  

$=\left(3-5\right)x^6+\left(-\sqrt{2}+2\sqrt{2}\right)x^5+2\sqrt{2}{x}^3+\left(8-4\right)x+1=$  

$-2x^6+\sqrt{2}{x}^5+2\sqrt{2}{x}^3+4x+1$  

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$d\text{)}W\left(x\right)-P\left(x\right)=\sqrt{2}{x}^4-3\sqrt{3}{x}^3+4x^2+1-\left(x^4-x^3+\sqrt{3}{x}^2-\sqrt{2}\right)=$  

$=\sqrt{2}{x}^4-3\sqrt{3}{x}^3+4x^2+1-x^4+x^3-\sqrt{3}{x}^2+\sqrt{2}=$  

$=\left(\sqrt{2}-1\right)x^4+\left(1-3\sqrt{3}\right)x^3+\left(4-\sqrt{3}\right)x^2+1+\sqrt{2}$