5. Problema de Comida: En una fiesta, hay \( x \) personas. Cada persona trae 3 bocadillos. Si se han traído un total de 27 bocadillos, ¿cuántas personas hay en la fiesta? - Ecuación: \( 3 \mathbf{x}=\mathbf{2 7} \)

3.2 Матрицы \( 3^{*} 3 \) 1. \( \left(\begin{array}{ccc}12 & 5 & 6 \\ -13 & 2 & 5 \\ 1 & 8 & -9\end{array}\right) \cdot X \cdot\left(\begin{array}{ccc}0 & 3 & 10 \\ -9 & -6 & -11 \\ 12 & 1 & 10\end{array}\right)=\left(\begin{array}{ccc}-1314 & 267 & -428 \\ 2472 & 89 & 718 \\ -1716 & 409 & 522\end{array}\right) \)

○39.5. а) \( \left\{\begin{array}{l}x-3 y=5, \\ 3 x+2 y=4 ;\end{array}\right. \) б) \( \left\{\begin{array}{l}3 x+y=1, \\ 2 x-5 y=-22 ;\end{array}\right. \) о39.6. а) \( \left\{\begin{array}{l}x+y=4, \\ 4 x-5 y=7 ;\end{array}\right. \) б) \( \left\{\begin{array}{l}x-y=6, \\ 5 x-2 y=-3 ;\end{array}\right. \) о39.7. а) \( \left\{\begin{array}{l}40 x+3 y=-10, \\ 20 x-7 y=-5 ;\end{array}\right. \) б) \( \left\{\begin{array}{l}5 x+2 y=1, \\ 15 x+3 y=3 ;\end{array}\right. \)

Write an equation that expresses the following relationship. \( u \) varies directly with \( p \) and inversely with \( d \) In your equation, use \( k \) as the constant of proportionality. पा]

b. \( x^{2}+2 x=15 \)

d. \( 2 x^{2}+27=-21 x \)