I'm suposed to use the substitution method for system of equations?

Question

3x - y = 9
2x + y = 11


(4,2)

I can use some help in understanding the steps in finding the answer, thanks.

Thank you singing rose, that was perfect.

Answer 1

Solve for "x" or, "y" in either equation. Let's solve for "x" in the 1st equation. Let's solve for "y" in the 2nd equation

First: subtract 2x from both sides (when you move a term to the opposite side, always use the opposite sign).

2x - 2x + y = 11 - 2x
y = 11 - 2x

Sec: replace 11 - 2x with the "y" variable in the 1st equation.

3x - (11-2x) = 9
3x - 11 - (-2x) = 9
3x - 11 + 2x = 9
5x - 11 = 9 > *Add 11 with both sides.

5x - 11 +11= 9 +11
5x = 20 > *Divide both sides by 5.

5x/5 = 20/5
x = 4

Third: replace 4 with the "x" variable in the 2nd equation.

2(4) + y = 11
8+y = 11 > *Subtract 8 from both sides.

8-8+y = 11-8
y = 3

Solution (4,3)
P.S. The solution is not (4,2)

Answer 2

Simple. You have 2 equations and 2 unknowns. To solve system of equations make sure you have the same about of equations as you do unknowns.

Pick one equation, one variable from that equation and solve for it.

3x+y=9: solving for y

y = -9 + 3x

Now substitute that into the next equation for y. That will give you only x as the unknown in the equation.

2x-9+3x=11

x = 4

Then go back to your original equation and plug your findings into x and solve for y:

y = 3

Answer 3

The correct answer is x=4, y=3.

Using the first equation, get y on one side by itself:

y=3x-9 (***)

Now substitute y into the second equation:

2x+(3x-9)=11

Solve for x, and then get y using (***) above.

Answer 4

It is easier to ADD:-
5x = 20
x = 4

8 + y = 11
y = 3
Answer is (4 , 3)

Substitution method:-
y = 11 - 2x

3x - (11 - 2x) = 9
5x - 11 = 9
5x = 20
x = 4 and y = 3
Answer is (4 , 3)