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Plugging In: Basic Technique

If $$2x=4y=z$$, what is $$x - y$$ in terms of $$z$$?
Correct. [[snippet]] Your **goal value** is what the question asks for: >$$x-y = 4-2 = \color{blue}{2}$$. Replace $$z$$ with 8 in the answer choices, and eliminate any answer choices that don't equal 2: >A) $$~ \frac{z}{4} = \frac{8}{4} = \color{blue}{2}$$. Don't eliminate. >B) $$~ \frac{z}{2} = \frac{8}{2} = \color{red}{4}$$. Eliminate. >C) $$~z=\color{red}{8}$$. Eliminate. >D) $$~2z=2(8)=\color{red}{16}$$. Eliminate. >E) $$~4z=4(8)=\color{red}{32}$$. Eliminate. Answer choice A is the only one that matches the goal value, and so it must be the right answer choice.
Incorrect. [[snippet]] Your **goal value** is what the question asks for: >$$x-y = 4-2 = \color{blue}{2}$$. If you try $$z=8$$ in this answer choice, it will not match your goal value. >$$ \frac{z}{2} = \frac{8}{2} = \color{red}{4}$$. Eliminate.
Incorrect. [[snippet]] Your **goal value** is what the question asks for: >$$x-y = 4-2 = \color{blue}{2}$$. If you check $$z=8$$ in this answer choice, it doesn't match your goal value. >$$z = \color{red}{8}$$. Eliminate.
Incorrect. [[snippet]] Your **goal value** is what the question asks for: >$$x-y = 4-2 = \color{blue}{2}$$. Since you used $$z=8$$ as your Plug-In, the correct answer will match your **goal value** for $$z=8$$. That is not the case here. >$$2z = 2(8) = \color{red}{16}$$. Eliminate.
Incorrect. [[snippet]] Your **goal value** is what the question asks for: >$$x-y = 4-2 = \color{blue}{2}$$. If you try $$z=8$$ in this answer choice, it will not match your goal value. >$$4z = 4(8) = \color{red}{32}$$. Eliminate.
$$ \frac{z}{4}$$
$$ \frac{z}{2}$$
$$z$$
$$2z$$
$$4z$$