SOLUTION: Hi my name is Caroline, I have a question on solving systems by substitution. How do I know whether to plug the first equation in for y or x? For example: y= 2x +4 x=y-3 I k

Algebra ->  Expressions-with-variables -> SOLUTION: Hi my name is Caroline, I have a question on solving systems by substitution. How do I know whether to plug the first equation in for y or x? For example: y= 2x +4 x=y-3 I k      Log On


   

Question 819987: Hi my name is Caroline,
I have a question on solving systems by substitution. How do I know whether to plug the first equation in for y or x? For example:
y= 2x +4
x=y-3
I know I have to plug in the 2x+4 into the second equation, I just don't know where! Any help would be appreciated!
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

y = 2x +4

 x = y-3  ****

 x = (2x+4) - 3    |Substituting  (2x+4)  for y

 x = 2x + 1     |Solving for x

 -1 = x   AND y  = 2    2%28-1%29%2B4%29

CHECKING our answer***

 -1 = 2-3 = -1