Final answer:
The student's response is incorrect if they solved for y and substituted it back into the first equation instead of substituting it into the second equation to solve a system of equations.
Step-by-step explanation:
If Marta solved for y in the first equation and then incorrectly substituted it back into the same equation, rather than substituting into the second equation in a system of equations, then the student's response is incorrect. When solving a system of equations, one technique is to solve one equation for one variable and then substitute that expression into the other equation to solve for the second variable. This method is known as substitution. The idea is to turn a system of two equations into one equation with a single variable.
If the correct solution to the problem was supposed to be an ordered pair (which seems to be missing from the question), then the correct process would involve substituting the expression for y into the second equation, not the first. Doing so allows for solving for x and then using the value of x to find the value of y. If the student did not do this, then their answer would not match the correct solution to the system of equations.