Solve for both systems 5x+6y=104 and 9x - y = 81

9x - y = 81

9x - y+y = 81+y

9x= 81+y

9x-81= 81-81+y

9x-81=y

5x+6y=104

5x+6(9x-81)=104

5x+6(9x) (6)(-81)=104

5x+54x -486=104

59x -486=104

59x -486+486=104 +486

59x=590

59x/59=590/59

x=10

9x-81=y

9(10)-81=y

90-81=y

9=y