### Home > CCAA8 > Chapter 4 Unit 5 > Lesson CCA: 4.2.4 > Problem4-71

4-71.

Solve these systems of equations using any method. Check each solution, if possible.

1.  $2 x + 3 y = 9 \\ - 3 x + 3 y = - 6$

• One strategy to solve this system of equations is to multiply the bottom equation by $-1$ so you can eliminate.

$2x+3y=9$
$3x-3y=6$
$5x=15$

After finding $x$, plug in its value into one of the equations to find the value of $y$.

$x=3$
$y=1$

1.  $x=8-2y\\y-x=4$

• Because one of the equations above is already solved for $x$, one strategy to solve this system is to substitute the first equation in for $x$ in the second equation.

1.  $y = - \frac { 1 } { 2 } x + 7 \\ y = x - 8$

• Use the Equal Values Method.

1.  $9 x + 10 y = 14 \\ 7 x + 5 y = - 3$

• Refer to part (a).

$x=-4;y=5$