6) Plantear un sistema de ecuaciones y resolver la siguiente situación: "Tomás utiliza en el gimnasio nueve pesas, siendo algunas de 5 kg y otras de 10kg. ¿Cuántas pesas de cada tipo utiliza si en total levanta 65 kg ?"

Simplify the expression. \( \frac{4 x^{2}-64}{16 x-64} \) Select the correct choice below and fill in any answer boxes in your choice. A. \( \frac{4 x^{2}-64}{16 x-64}=\square \) (Simplify your answer. Use integers or fractions for any numbers in the expression.) B. The expression cannot be simplified.

L- Simplify the expression. \[ \frac{x^{3}+9 x^{2}}{x^{2}+5 x-36} \] Select the correct choice below and fill in any answer boxes in your choice. A. \( \frac{x^{3}+9 x^{2}}{x^{2}+5 x-36}=\square \) (Simplify your answer.) B. The expression cannot be simplified.

Simplify the expression. \( \frac{36-x^{2}}{x-6} \) Select the correct choice below and fill in any answer boxes in your choice. A. \( \frac{36-x^{2}}{x-6}=\square \) (Simplify your answer.) B. The expression cannot be simplified.

Simplify the expression. \( \frac{z^{2}+z x+2 z+2 x}{z+2} \) Select the correct choice below and fill in any answer boxes in your choice. A. \( \frac{z^{2}+z x+2 z+2 x}{z+2}=\square \) (Simplify your answer.) B. The expression cannot be simplified.

Simplify the expression. \[ \frac{2 x y+7 x-2 y-7}{9 x y+8 x-9 y-8} \] Select the correct choice below and fill in any answer boxes in your choice. A. \( \frac{2 x y+7 x-2 y-7}{9 x y+8 x-9 y-8}=\square \) (Simplify your answer.) B. The expression cannot be simplified.