Question

Solve using substitution. x + 3y = -13 5x + 7y = -9

Answer 1

X+3y=-13
x=-3y-13
5(-3y-13) +7y = -9 
-15y -65 +7y = -9 
-8y-65=-9
             65 -
             -----
             -74
              /-8
             ------
  y=       9.25

x+3(9.25) = -13
x+27.75= -13
             27.75-
             -------
x=        -40.75

Answer 2

Just add -3y to both of the sides:

x + 3y + -3y = -13 + -3y

x = -3y - 13

Our Answer:

x = -3y - 13
_______________________________________________________

Add -7y to both of the sides.

5x + 7y + -7y = -9 + -7y

5x = -7y - 9

Then, divide both by 5.

5x
___    = -7y - 9 
5       _____
             5



Our Answer:  5x
                      ___ = - 7y -9
                       5       _____
                                     5
                       
 _________________________________________________________      

Hope This Helps!!!