\( \left. \begin{array} { c } { x + y + z = 6 } \\ { \left. \begin{array} { c } { 3 x - 2 y + 6 z = 11 } \\ { x + z = 7 } \end{array} \right. } \end{array} \right. \Rightarrow \left[ \begin{array} { c c c c } { 1 } & { 1 } & { 1 } & { 6 } \\ { 3 } & { - 2 } & { 6 } & { 1 } \\ { 1 } & { 0 } & { 1 } & { 7 } \end{array} \right] \)

How much pure acid should be mixed with 2 gallons of a \( 50 \% \) acid solution to get an \( 80 \% \) acid solution?

QUESTION 12 If \( 2^{x} 5^{y}=16 \times 125 \), where \( x \) and \( y \) are positive integers, determine \( x-y \) :

\( x^{2}-(k+3) x-7=0 \) seja igual a 8

\( f(x)=5 x+6 ; g(x)=3 x-2 \) (h) Find \( \left(\left.\bar{g}\right|^{(1)}\right. \) \( \left(\frac{f}{g}\right)(1)=\square \) (Type an integer or a simplified fraction.)

Simplify he following fully: \( \frac{3^{3+1}-3^{-1}}{23^{x}} \) \( \frac{3^{x} \cdot 3^{1}-3^{x} \cdot 3^{-1}}{2 \cdot 3^{x}} \frac{3^{x}\left(1-\frac{1}{3}\right)}{23^{x}} \)