To solve the equation 2x = y and y - 3x = -5 using substitution, what is the first step?

To solve the equations (2x = y) and (y - 3x = -5) using substitution, starting by substituting (y) in the second equation is the best initial step. This approach takes advantage of the first equation where (y) is expressed in terms of (x).

By substituting (y) with (2x) in the equation (y - 3x = -5), you will replace (y) with the value from the first equation. This leads to a single equation in one variable (specifically, (x)), which is easier to solve. Once this substitution is made, you can solve for (x) and then use that value to find (y).

Other strategies, like multiplying both equations or adding them together, do not directly facilitate solving the system through substitution as effectively as replacing (y) in the second equation does. Making (x) the subject in the first equation as a first step would also not take full advantage of the clear substitution already defined.