We have substituted equation 1 into equation 2 by replacing the y in 2 by 4x3 from 1. Then you have to divide the whole equation by whatever your number is. A simultaneous equation has a general form which is written as ax by c.
The same has been done in the example with equation 1 and 2.
The simultaneous equation is an equation with two or more unknown value which the value of the unknown is same to the other equation. To solve a pair of simultaneous equations first eliminate one of the letter terms and find the value of the remaining letter. In simple terms the solution to a pair of simultaneous equations is the x and y values of the coordinates of the point at which the graphs cross or intersect. The example below shows this.