If Martha earns three times as much as Sharon, who earns 25% of Samantha's earning, Sharon's earning constitutes what percent of the total earning of all three?

Incorrect.
[[snippet]]

Incorrect.
[[snippet]]

Incorrect.
[[snippet]]

Correct.
[[snippet]]
Start by __Plugging In__ for the smallest invisible variableâ€”in this case, Sharon's earnings. Use a good number, like 2. If Sharon earns $2, then Samantha earns $$4\times 2=\$8$$ and Martha earns $$3\times2=\$6$$.
Their total earnings are $$2+6+8=\$16$$. Therefore, Sharon's earnings equal $$\frac{2}{16} = \frac{1}{8}$$, or 12.5%, of the lot.
__Alternative explanation__:
Since the problem uses percents and not real numbers, __Plug In__ 100. Make the $100 the number you're taking the percent from. In this case, Sharon's earnings are 25% of Samantha's earnings. Assume that Samantha earns $100 so that Sharon earns $25 and Martha earns $$3\cdot 25 = \$75$$.
Using these numbers, Sharon earns $25 out of a total of $$100+25+75 = \$200$$. Translate this fraction into percents by multiplying by 100:
>$$\displaystyle \require{cancel}\require{enclose} \frac{25}{200} = \frac{25}{200} \times 100\% = \frac{25}{2}\% = 12.5\%$$.

Incorrect.
[[snippet]]

10%

12.5%

15%

20%

25%