To determine which of the given expressions is equal to [tex]\(\frac{3}{\sqrt{7}}\)[/tex], let's go through each option step by step for comparison.
### Given Expression:
[tex]\[
\frac{3}{\sqrt{7}} \approx 1.1339
\][/tex]
### Option 1: [tex]\(\frac{3 \sqrt{7}}{7}\)[/tex]
[tex]\[
\frac{3 \sqrt{7}}{7} \approx 1.1339
\][/tex]
This value is approximately the same as the given expression.
### Option 2: [tex]\(\frac{7}{3 \sqrt{7}}\)[/tex]
[tex]\[
\frac{7}{3 \sqrt{7}} \approx 0.8819
\][/tex]
This value is different from the given expression.
### Option 3: [tex]\(\frac{3 \sqrt{7}}{49}\)[/tex]
[tex]\[
\frac{3 \sqrt{7}}{49} \approx 0.1620
\][/tex]
This value is different from the given expression.
### Option 4: [tex]\(\frac{21}{\sqrt{7}}\)[/tex]
[tex]\[
\frac{21}{\sqrt{7}} \approx 7.9373
\][/tex]
This value is different from the given expression.
Based on these calculations, the expression that is equal to [tex]\(\frac{3}{\sqrt{7}}\)[/tex] is:
[tex]\[
\boxed{\frac{3 \sqrt{7}}{7}}
\][/tex]
