Solve the System: Equations 6x + 4y = 18 and -2x + 3y = 20

System of Equations with Elimination Method

6x+4y=18 6x+4y=18

2x+3y=20 -2x+3y=20

❤️ Continue Your Math Journey!

We have hundreds of course questions with personalized recommendations + Account 100% premium

Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Solution
00:03 Let's multiply one of the equations by 3, so we can combine them
00:16 Now let's combine the equations
00:21 Let's reduce what we can
00:29 Let's group terms
00:37 Let's isolate Y
00:46 This is the value of Y
00:55 Now let's substitute Y to find the value of X
01:15 Let's isolate X
01:24 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

6x+4y=18 6x+4y=18

2x+3y=20 -2x+3y=20

2

Step-by-step solution

To solve this problem, we'll use the elimination method:

  • Step 1: Align the coefficients of x x to eliminate it.
  • Step 2: Subtract one equation from the other to solve for the remaining variable.
  • Step 3: Substitute the known variable back into one of the original equations to find the value of the second variable.

Now, let's work through each step:

Step 1: The given system of equations is:

6x+4y=18 6x + 4y = 18 (Equation 1)

2x+3y=20 -2x + 3y = 20 (Equation 2)

To eliminate x x , we want the coefficients of x x to be equal in magnitude. Multiply Equation 2 by 3 to match the x x coefficient in Equation 1:

3(2x+3y)=3(20) 3(-2x + 3y) = 3(20)

This results in:

6x+9y=60-6x + 9y = 60 (Equation 3)

Step 2: Add Equation 1 and Equation 3 to eliminate x x :

(6x+4y)+(6x+9y)=18+60 (6x + 4y) + (-6x + 9y) = 18 + 60

This simplifies to:

13y=78 13y = 78

Solving for y y , we divide both sides by 13:

y=7813=6 y = \frac{78}{13} = 6

Step 3: Substitute y=6 y = 6 back into Equation 1:

6x+4(6)=18 6x + 4(6) = 18

6x+24=18 6x + 24 = 18

Subtract 24 from both sides:

6x=1824 6x = 18 - 24

6x=6 6x = -6

Divide both sides by 6:

x=66=1 x = \frac{-6}{6} = -1

Therefore, the solution to the system of equations is x=1,y=6\mathbf{x = -1, y = 6}.

3

Final Answer

x=1,y=6 x=-1,y=6

Key Points to Remember

Essential concepts to master this topic
  • Strategy: Multiply equations to create equal opposite coefficients for elimination
  • Technique: Multiply -2x + 3y = 20 by 3 to get -6x + 9y = 60
  • Check: Substitute x = -1, y = 6: 6(-1) + 4(6) = 18 and -2(-1) + 3(6) = 20 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to multiply the entire equation when scaling
    Don't multiply just one term like changing -2x + 3y = 20 to -6x + 3y = 20 = wrong equation! This breaks the mathematical balance and gives incorrect solutions. Always multiply every term including the constant on the right side.

Practice Quiz

Test your knowledge with interactive questions

\( \begin{cases} x+y=8 \\ x-y=6 \end{cases} \)

FAQ

Everything you need to know about this question

Why multiply equation 2 by 3 instead of equation 1?

+

We want to eliminate x by making coefficients opposites. Since equation 1 has 6x 6x and equation 2 has 2x -2x , multiplying by 3 gives us 6x -6x , which is the opposite of 6x 6x !

Could I eliminate y instead of x?

+

Absolutely! You could multiply equation 1 by 3 and equation 2 by 4 to get 12y 12y and 12y 12y , then subtract. Both methods give the same answer: x=1,y=6 x = -1, y = 6 .

How do I know which variable to eliminate first?

+

Choose the variable that requires smaller multipliers. In this problem, eliminating x only needs multiplying by 3, while eliminating y needs multiplying by both 3 and 4.

What if I get different answers using substitution method?

+

If you do the substitution method correctly, you'll get the same answer! Try solving 2x+3y=20 -2x + 3y = 20 for x, then substitute into the first equation.

Why does adding the equations eliminate x?

+

Because 6x+(6x)=0 6x + (-6x) = 0 ! When you have equal and opposite coefficients, they cancel out completely, leaving you with an equation in just one variable.

How can I check if my solution is correct?

+

Substitute x=1 x = -1 and y=6 y = 6 into both original equations. You should get 18 = 18 and 20 = 20. If both check out, your solution is right!

🌟 Unlock Your Math Potential

Get unlimited access to all 18 System of linear equations questions, detailed video solutions, and personalized progress tracking.

📹

Unlimited Video Solutions

Step-by-step explanations for every problem

📊

Progress Analytics

Track your mastery across all topics

🚫

Ad-Free Learning

Focus on math without distractions

No credit card required • Cancel anytime

More Questions

Click on any question to see the complete solution with step-by-step explanations