The first method involves substituting for one variable using one of the equations and reducing the system of equations in 2 variables to an equation in one variable. Let us see how it is done using an example.
We would like to reduce them to a single linear equation in x by using the first equation to express y in terms of x. That is, we bring all the y terms of the equation to one side of the equals sign as follows.
X equals 2y plus 1 becomes
(x minus 1) over 2 equals y.
Now we can substitute for y in the second equation using this expression.
That is,
X plus y equals 4 becomes
X plus ((x minus 1) over 2) equals 4.
Simplifying, this gives
(2x plus x minus 1) over 2, equals 4 or
3x equals 8 plus 1
Thus x equals 9 divided by 3 which is 3.
Now with the value 3 of x, we may substitute this value in either of the 2 equations to get the value of y. Let’s use the first equation.
3 equals 2y plus 1.
Or 2 equals 2y
Which gives y to be 2 over 2 which is 1.
Thus the solution for this system of linear equations in 2 variables x and y is :
X equals 3 and y equals 1.