a) Pt ⇔ $\frac{2x}{4}-$ $\frac{10}{4}=5+$ $\frac{2}{6}$ $-\frac{3x}{6}$
⇔$\frac{2x}{4}+\frac{3x}{6}=5+\frac{2}{6}+\frac{10}{4}$
⇔$x=\frac{47}{6}$
b) $(x-3)(3-4x)+(x-3)^2=0$
⇔$(x-3)(3-4x+x-3)=0$
⇔$(x-3)(-3x)=0$
⇔\(\left[ \begin{array}{l}x=3\\x=0\end{array} \right.\)
c) Pt⇔$\frac{x-90}{10}-1+$ $\frac{x-76}{14}-2+$ $\frac{x-58}{14}-3+$ $\frac{x-36}{16}-4+$ $\frac{x-15}{17}-5=0$
⇔$\frac{x-100}{10}+\frac{x-100}{12}+\frac{x-100}{14}+\frac{x-100}{16}+\frac{x-100}{17}=0$
⇔$(x-100)(\frac{1}{10}+\frac{1}{12}+\frac{1}{14}+\frac{1}{16}+\frac{1}{17})=0$
$⇔x-100=0$
⇔$x=100$
