(6) \( \left\{\begin{array}{l}7 x-8=-5 y \\ y=4-3 x\end{array}\right. \)

(i) \( 2.25 \% \) of \( x \) is 630

Simplify the following: (1) \( \frac{x-1}{x^{2}+3 x+2} \div\left[\frac{x-3}{x+1}-\frac{x-4}{x+2}\right] \) (2) \( \frac{\frac{6 x+5}{x-5}-1}{\frac{3 x+20}{x-5}+2} \) (3) \( \frac{a^{2}+\left(1-a^{2}\right)}{(1+a) a} \times \frac{(1+a) a}{a^{2}-\left(1-a^{2}\right)} \)

\begin{tabular}{l} Evaluate the expression when \( c=8 \) and \( d=4 \). \\ \( \qquad \frac{48}{c}+d \) \\ \( \square \square \) \\ \hline\( \square \) \\ \hline\end{tabular}

Evaluate the expression when \( a=6 \) and \( b=27 \). \[ b-4 a \] \( \square \) \begin{tabular}{ccc}\hline\( \square \) & 5 \\ \hline\end{tabular}

Utiliza logaritmos para resolver: \( 5^{x} = 125 \).