91Ó°ÊÓ

The average (arithmetic mean) of the test scores of a class of x students is 74, and the average of the test scores of a class of y students is 88. When the scores of both classes are combined, the average is 76. What is the value of $\frac{x}{y}$?

Solve each system of equations.

$\begin{array}{c}x+z=7\\ 2y−z=−3\\ −x−3y+2z=11\end{array}$

Solve the system of equations by graphing.

$\begin{array}{c}-2x-6y=0\\ 3x+11y=4\end{array}$

Solve each system of equations

$\begin{array}{l}4a−2b+8c=30\\ a+2b−7c=−12\\ 2a−b+4c=15\end{array}$

Solve the system of equations by graphing.

$\begin{array}{c}3x-5y=-13\\ 4x+2y=0\end{array}$

Solve each system of inequalities by graphing.

$\begin{array}{c}\text{3}y≤2x−8\\ yâ‰\yen \frac{2}{3}x−1\end{array}$

Compare the quantity in Column A and the quantity in Column B. Then determine whether:

(A) The quantity in Column A is greater,

(B) The quantity in Column B is greater,

(C) The two quantities are equal, or

(D) The relationship cannot be determined from the information given.

19.

Column A: The percent increase from 75 to 100.

Column B: The percent decrease from 100 to 75.

Solve each system of equations by using elimination

$\begin{array}{c}19.\text{ â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰}u+v=7\\ \text{ â¶Ä‰â¶Ä‰â¶Ä‰â¶Ä‰â€‰â€‰â€‰â€‰}2u+v=11\end{array}$

Graph each system of inequalities. Name the coordinates of the vertices of the feasible region. Find the maximum and minimum values of the given function for this region

$\begin{array}{c}19.y≤x+2\\ y≤11−2x\\ 2x+yâ‰\yen −7\\ f(x,y)=4x−3y\end{array}$

Solve each system of equations by graphing.

19.$\begin{array}{c}\text{2}x+3y=7\\ 2x−3y=7\end{array}$