2x - 6y = 18
4x + 3y = 6
First, make either the x or y the same value by multiplying the equations. Let's choose x.
2x - 6y = 18 x2
4x + 3y = 6 x1
(+)4x - 12y = 36
(+)4x + 3y = 6
Now, we use the rule of 'same sign subtract', 'different sign add'. As the signs are the same in this example, we will subtract the equations.
-15y = 30
Now, we must divide both sides by -15 in order to isolate the y.
y = 30/-15
y = -2
We must then substitute the value for y into one of the equations to find x.
4x + 3y = 6 (substitute y = -2)
4x + 3(-2) = 6
4x - 6 = 6
Now we must add 6 to both sides to get the 4x on its own.
4x = 12
Then divide both sides by 4 to find the value of x.
x = 12/4
x = 3
We can then check our values (x = 3, y = -2) are correct by substituting them into the other equation.
4x + 3y = 6 (substitute x = 3, y = -2)
4(3) + 3(-2) = 6
12 - 6 = 6
6 = 6
This means that we successfully solved the simultaneous equation.