If Mark saves 50% more than Sally every month, Sally's annual savings are approximately what percent of Mark's annual savings?

Incorrect.
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Correct.
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It is always better to start with the smallest variable, so make Sally's monthly savings the invisible variable. When the problem asks about percents, use 100. So if Sally saves $100 per month, Mark saves 50% more (i.e., $150). Now pause for a moment. Did you multiply Sally's and Mark's savings by 12 (months)?

Incorrect.
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Incorrect.
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Incorrect.
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There's really no need to multiply Mark's or Sally's savings. If Mark saves 50% more than Sally does every month, it is the same for a whole year's savings. Save yourself the trouble and work with smaller numbers. The question is actually a percent translation sentence.
And so, {color:purple}"Sally's annual savings are approximately what percent of Mark's annual savings?"{/color} translates into
>$$\displaystyle 100=\frac{x}{100}\cdot150$$.
Reduce $$\frac{150}{100}$$ by 50 to $$\frac{3}{2}$$ and solve for $$x$$:
>$$\displaystyle 100 = \frac{3x}{2}$$
>$$\displaystyle 200 = 3x \hspace{0.3in}$$ [Multiply by 2]
>$$\displaystyle \frac{200}{3} = x \hspace{0.4in}$$ [Divide by 3]
>$$\displaystyle x=\frac{200}{3} \approx 66.7$$.

25%

33%

50%

67%

75%

Of course I did. How else can I answer the question?

No, I didn't. There's no need.