We need to find the variables having equal coefficients or make the coefficients of some variable equal because we will be able to eliminate a variable. For eg. take the following pair of linear equations.
=> x + y = 14 (Eq. 1) => x - y = 4 (Eq. 2)
As we see, the coefficients of x and y are same but in y, the coefficients are +1 and -1 which can be easily cancelled while adding the equations. This will eliminate the variable y. So, we can find the value of x and then substitute it in any equation to find the value of y.
