3 3/4:1 =20:х

To solve the proportion \( \frac{3 \frac{3}{4}}{1} = \frac{20}{x} \), we first convert \( 3 \frac{3}{4} \) to an improper fraction:

\[ 3 \frac{3}{4} = \frac{3 \times 4 + 3}{4} = \frac{12 + 3}{4} = \frac{15}{4} \]

Now we rewrite the equation:

\[ \frac{15/4}{1} = \frac{20}{x} \]

This simplifies to:

\[ \frac{15}{4} = \frac{20}{x} \]

Next, we can cross-multiply to solve for \( x \):

\[ 15x = 20 \times 4 \]

Calculating the right-hand side:

\[ 20 \times 4 = 80 \]

So we have:

\[ 15x = 80 \]

Now, divide both sides by 15 to isolate \( x \):

\[ x = \frac{80}{15} \]

We can simplify this fraction:

\[ x = \frac{16}{3} \]

Thus, the value of \( x \) is:

\[ x = 5 \frac{1}{3} \quad \text{or} \quad x = \frac{16}{3} \]