Question

Solve each system using substitution. Tell whether the system has one solution, infinitely many solutions, or no solution.

13. -x + y = -13
3x - 1 = 19

15. 1/3y= 7/3 x + 5/3
x - 3y = 5

17. 3x + y = -13
-2x + 5y = -54

Answer 1

13. -x + y = -13
3x - 1 = 19
Is that a typo? No y in second equation? That sure makes it easy.

15.
y = (7 x + 5)
x - 3(7x+5) = 5
x - 21 x - 15 = 5
-20 x = 20
x = -1
y = -2

17.
y = (-3x - 13)

-2x + 5 (-3x-13) = -54
or
2x + 5 (3x+13) = 54
17 x + 65 = 54
17 x = - 11
x = -11/17
y = 33/17 -13 = 33/17 - 221/17 = -188/17

Answer 2

I don't get it. What do you mean?

Answer 3

Oh thanks ! and for number one that's how the equations was written

Answer 4

Oh yeah sorry. i didn't see it. for number one it was 3x-y=19

Answer 5

13.
-x + y = -13
3x - y = 19
--------------- too easy to add them
2 x + 0 = 6
x = 3
y = -10

Answer 6

Thank you so much can you help me with couple more?

Answer 7

Do not do it the way I did it. Use substitution, but you should get the same answer.

Answer 8

You should be able to do them yourself now.