The equation (y + 5) + y = 6 shows the substitution method being used to solve the system of linear equations. So the correct option among all the options given in the question is option "D". For a better explanation, let us first write down the two equations given in the question. x + 5 = 6 and x = y + 5 Now the thing that has been done is that the value of x in the first equation has been replaced by the value of x that is given in the second equation. this is actually the substitution method of solving equations.
