7:28=5,5:4x

To solve the proportion \( \frac{7}{28} = \frac{5}{4x} \), cross-multiply to find the value of \( x \):

\[ 7 \cdot 4x = 28 \cdot 5 \]

\[ 28x = 140 \]

Divide both sides by 28:

\[ x = \frac{140}{28} \]

\[ x = 5 \]

So, the value of \( x \) is 5.