12) Para que o sistema \[ \left\{\begin{array}{r}x+y=6 \\ 2 x+a y=10\end{array}\right. \] Seja impossível, calcule o valor de a.

Which of the following equations has no solution \( \begin{array}{l}x+20-5 x=7(3+x)-3 x \\ \begin{array}{l}5 x+20-7 x=7(3+x)-3 x \\ 5 x+21-x=7(3+x)-3 x \\ 5 x+20-x=7(3+x)-3 x\end{array} \\ \begin{array}{l}5\end{array}\end{array} \$ \begin{array}{l}\text { - }\end{array} \)

a) \( \log _{2} x=1-x \);

a) \( \log _{2} x=1-x \);

Suppose the linear regression line \( y=3.009 x \) - 77.131 predicts a pizza parlor's profits based on the number of pizzas sold. If \( x \) represents the number of pizzas sold, and \( y \) represents the pizza partor's profits in dollars, about how much can the plizza parlor expect in profits if it sells 275 pizzas? A. \( \$ 750 \) B. \( \$ 900 \) C. \( \$ 825 \) D. \( \$ 675 \)

Which of the following equations has no solution? \( \begin{array}{c}5 x+20-7 x=7(3+x)-3 x \\ x+20-5 x=7(3+x)-3 x \\ 5 x+21-x=7(3+x)-3 x \\ 5 x+20-x=7(3+x)-3 x\end{array} \)