7,2:88,2=0,4:x

To solve the proportion \( \frac{7.2}{88.2} = \frac{0.4}{x} \), you can use cross-multiplication.

Cross-multiplying gives us:

\[ 7.2 \cdot x = 0.4 \cdot 88.2 \]

Calculating the right side:

\[ 0.4 \cdot 88.2 = 35.28 \]

Now, we have:

\[ 7.2x = 35.28 \]

To find \( x \), divide both sides by 7.2:

\[ x = \frac{35.28}{7.2} \]

Calculating the division:

\[ x = 4.9 \]

Thus, the value of \( x \) is \( 4.9 \).