Let's solve the equation step by step:

1. First part: $\frac{3}{24}$
   $\frac{3}{24} = 0.125$

2. Second part: Multiply by 21
   $0.125 \times 21 = 2.625$

So the correct decimal answer is $2.625$.

To express this as a fraction:

• $2.625$ can be written as a mixed fraction: $2.625 = 2 \frac{5}{8}$

Thus, the fraction form of $2.625$ is $2 \frac{5}{8}$ or $\frac{21}{8}$.

For measurement:

• In cups, $\frac{21}{8}$ cups is the exact measurement, which is equivalent to 2 cups and 5/8 of a cup.

Final answers:

• Decimal: $2.625$
• Fraction: $\frac{21}{8}$ or $2 \frac{5}{8}$

Would you like further details or clarification on any part of this? Here are some related questions:

1. How is $2.625$ converted into a fraction?
2. What is the process of multiplying decimals by whole numbers?
3. How do mixed fractions relate to cooking measurements?
4. Why is $\frac{21}{8}$ useful for measuring in cups?
5. How do you convert between decimal and fraction measurements in recipes?

Tip: When converting decimals to fractions, break down the decimal into its fractional components and simplify!