Answers and Steps for the Example Problems

· 2x+3y=5, x-5y=9

x-5y+5y=9+5y

x=9+5y

2x+3y=5

2(9+5y)+3y=5

18+10y+3y=5

18+13y=5

13y=-13

y=-1

x=9+5y

x=9+5(-1)

x=4

· x+2y=2, 7x-3y=-20

x+2y-2y=2-2y’

x=2-2y

7(2-2y)-3y=-20

14-14y-3y=-20

-17y=-34

y=2

x=2-2y

x=2-2(2)

x=2-4

x=-2

· 3x-y=4, 5x+3y=9

3x-y-3x=4-3x

-y=4-3x

y=3x-4

5x+3(3x-4)=9

5x+9x-12=9

14x=21

x=3/2

3(3/2)-y=4

9/2-y=4

-y=4-9/2

-y=8/2-9/2

-y=-1/2

y=1/2