Write down both of the equations that you'll need to solve. 3x - y = 12 2x + y = 13
Number the equations. 3x - y = 12 as number one, and 2x + y = 13 as number two.
Check if both equations have the same variable/unknown term in them.
Look for signs of the unknown variables or terms. Remember subtraction can also be referred to as the addition of a negative number. If the signs are the same, subtract both equations. If they are different then add the equations. 3x - y = 12 + 2x + y = 13 ------------- 5x = 25Solve Simultaneous Equations Using Elimination Method Step 4Bullet4.jpg
Solve to find the first unknown variable from the resulting (rather shortened) equation. Divide both sides by the coefficient of the left side. Take 5 to the other side.It will look like this:x = 25/5.
25 divided by 5 makes 5 so we have now found the value of "x" which is 5.
Find the value of "y". Use the value of x that was obtained above into either equation (but stick with this equation for the time being). Substitute this value of x into the equation. 3x - y = 12Solve Simultaneous Equations Using Elimination Method Step 7Bullet1.jpg 3(5)-y = 12Solve Simultaneous Equations Using Elimination Method Step 7Bullet2.jpg 15 - y = 12Solve Simultaneous Equations Using Elimination Method Step 7Bullet3.jpg - y = 12 - 15Solve Simultaneous Equations Using Elimination Method Step 7Bullet4.jpg - y = - 3(divide both sides by negative one, will be able to cut both signs)Solve Simultaneous Equations Using Elimination Method Step 7Bullet5.jpg y = 3Solve Simultaneous Equations Using Elimination Method Step 7Bullet6.jpg
Check the problem. Substitute both the values into the other equation. If the two side numbers at the very end equal each other, you've correctly solved this system of simultaneous equations. 3x - y = 12 3(5) - 3 = 12 15 - 3 = 12 12 = 12
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