Chapter 6 - Systems of Equations and Inequalities - 6-4 Applications of Linear Systems - Practice and Problem-Solving Exercises - Page 391: 17

$A=-3$ $B=-2$

$Ax — 2 By = 6 $ $3 Ax - By = -12 $ Plug in the values for x and y. $2A - 6B =6$ $6A -3B=-12$ Add 3 to both sides of the first equation: $6A - 18B =18$ $6A -3B=-12$ Eliminate: $-15B=30$ $B=-2$ Solve for A $A=-3$