Resposta:

Explicação passo a passo:

a

2x-y=3

x+y=3

_____

3x=6

x=6/3

x=2

x+y=3

3+y=3

y=3-2

y=1

b

x-3y=9

2x+3y=6

_______

3x=15

x=15/3

x=5

2x+3y=6

2.5+3y=6

10+3y=6

3y=6-10

3y=-4

y=-4/3

c

2.3y-4y=6

6y-4y=6

2y=6

y=6/2

y=3

x=3.3

x=9

d

2x-y=3

x+y=-1

_____

3x=-4

x=-4/3

x+y=-1

-4/3+y=-1

y=-1+4/3

y=-3/3+4/3

y=1/3

e

x-3y=9

2x+3y=6

_______

3x=15

x=15/3

x=5

x-3y=9

5-3y=9

-3y=9-5

-3y=4 (-1)

3y=-4

y=-4/3