Chapter 6 - Systems of Equations and Inequalities - Chapter Review - 6-3 and 6-4 Solving Systems Using Elimination; Applications of Systems - Page 406: 22

$(5,12)$ one solution

$9x+.5y = 51$ $7x+1/3y = 39$ $9x+.5y = 51$ $-7*(9x+.5y = 51)$ $-63x-3.5y = -357$ $7x+1/3y = 39$ $9(7x+1/3y = 39)$ $63x +3y = 351$ $-63x-3.5y+63x+3y = -357+351$ $-.5y = -6$ $-.5y*-2 = -6*-2$ $y = 12$ $9x+.5y=51$ $9x+.5*12 = 51$ $9x+6 = 51$ $9x+6-6 = 51-6$ $9x = 45$ $9x/9 = 45/9$ $x=5$