To determine the first step in solving the system of equations using the substitution method, we need to look at the equations provided (which are not explicitly listed in your question). However, I can guide you based on the options you've given.
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Substitute 11 - x for the x in the bottom equation: This indicates that you might have an equation in which you can express x in terms of another variable. It is often done if you have already isolated x.
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Substitute -y - 9 in for x in the top equation: Similar to the first option, this indicates that you've isolated x in the form of another expression involving y.
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Add the equations together: This step would typically be used in the elimination method rather than substitution.
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Substitute y = 11 in for x in the bottom equation: This implies that y is known, and you want to substitute it into an equation.
Given this context, if the goal is to use the substitution method, the most likely correct first step would be to substitute an expression for x or y based on one of the equations you have.
Without knowing the specific context of your equations, the best choice seems to be either of the first two options (substituting for x or y), depending on which variable has already been isolated. If I were to choose, I would lean toward the option that correlates most directly with the equations given.
If you can provide the actual equations, I would be able to give you a more definitive answer.