\(a,27\cdot3^{n-1}=81\\ \Rightarrow3^{n-1}=81:27\\ \Rightarrow3^{n-1}=3\\ \Rightarrow n-1=1\\ \Rightarrow n=2\)

\(b,5\cdot5^{6-n}=625\\ \Rightarrow5^{6-n}=625:5\\ \Rightarrow5^{6-n}=125\\ \Rightarrow5^{6-n}=5^3\\ \Rightarrow6-n=3\\ \Rightarrow n=3\)

\(\left(\dfrac{-5}{7}\right).\left(\dfrac{2}{5}-x\right)+\dfrac{-1}{3}=\dfrac{1}{5}+\dfrac{-3}{10}\\ \Rightarrow-\dfrac{5}{7}\cdot\dfrac{2}{5}+\dfrac{5}{7}\cdot x-\dfrac{1}{3}=\dfrac{1}{5}-\dfrac{3}{10}\\ \Rightarrow-\dfrac{2}{7}+\dfrac{5}{7}x-\dfrac{1}{3}=-\dfrac{1}{10}\\ \Rightarrow-\dfrac{13}{21}+\dfrac{5}{7}x=-\dfrac{1}{10}\\ \Rightarrow\left(\dfrac{5}{7}x\right)=-\dfrac{1}{10}+\dfrac{13}{21}\\ \Rightarrow\left(\dfrac{5}{7}x\right)=\dfrac{109}{210}\\ \Rightarrow x=\dfrac{109}{150}\)

\(\left(3x-21\right)\cdot\left(43-x\right)=0\\ \Rightarrow\left[{}\begin{matrix}3x-21=0\\43-x=0\end{matrix}\right.\\\Rightarrow\left[{}\begin{matrix}x=7\\x=43\end{matrix}\right. \)

Vậy: \(x=7;x=43\)

1435; 3192; 2307; 1435; 3192; 2307; 1435; 3192; 2307; 1435

Hiệu của \(2\) số là:

\(6\times2=12\)

Số lớn là:

\(\left(204+12\right):2=108\)

Số bé là:

\(108-12=96\)

Đáp số: Số lớn: 108; số bé: 96

I have no difficulty in the morning.

Dịch: Tôi không gặp khó khăn vào buổi sáng.

\(\left(x+\dfrac{1}{7}\right):\dfrac{1}{3}=\dfrac{3}{4}\\ \Rightarrow x+\dfrac{1}{7}=\dfrac{3}{4}\cdot\dfrac{1}{3}\\ \Rightarrow x+\dfrac{1}{7}=\dfrac{1}{4}\\ \Rightarrow x=\dfrac{1}{4}-\dfrac{1}{7}\\ \Rightarrow x=\dfrac{3}{28}\)

Vậy: \(x=\dfrac{3}{28}\)