SOLUTION: {3x+4y=9 y=x-3 it says to solve the system by using substitution idk how to do that... please help

Algebra.Com
Question 198719This question is from textbook The shapes of algebra
: {3x+4y=9
y=x-3

it says to solve the system by using substitution
idk how to do that... please help This question is from textbook The shapes of algebra

Answer by jim_thompson5910(35256)   (Show Source): You can put this solution on YOUR website!
Start with the first equation.


Plug in into the first equation. In other words, replace each with . Notice we've eliminated the variables. So we now have a simple equation with one unknown.


Distribute


Combine like terms on the left side


Add 12 to both sides


Combine like terms on the right side


Divide both sides by 7 to isolate x


Divide


Now that we know that , we can plug this into to find


Start with the second equation.


Plug in


Subtract


So our solutions are and which form the ordered pair



Notice if we graph the two equations, we can see that their intersection is at . So this verifies our answer.


Graph of (red) and (green)


RELATED QUESTIONS

I'm having a hard time understanding this system and I just need a break down of how to... (answered by stanbon)
how do you solve each system of simultaneous equations by using the substitution method. (answered by Fombitz)
It says to solve each system by substitution and elimination but I don't understand on... (answered by mananth,MathTherapy)
can you help me solve this equation? I am trying to solve a system of linear... (answered by xcentaur)
Directions: Solve each system of equations by the substitution method. Problem:... (answered by jim_thompson5910)
please help me it says to solve by using elimination method x + 8y = 14 -3x +... (answered by scott8148)
It says to solve the system of equations using the substitution method. x+y=1 3x+4y=1 (answered by elima)
solve the linear system by using substitution: x=4y+14 , y=-3x+3... (answered by stanbon)
It says to solve the following System of equations by either addition or substitution?? (answered by josgarithmetic,MathTherapy)