Solve for x

To solve the equation \( 20 = 5 - \frac{3}{8}x \), follow these steps:

1. Start by isolating the variable term. Subtract 5 from both sides:

\[
20 - 5 = -\frac{3}{8}x
\]

This simplifies to:

\[
15 = -\frac{3}{8}x
\]

2. To eliminate the negative sign and the fraction, multiply both sides by -1:

\[
-15 = \frac{3}{8}x
\]

3. Now, to solve for \( x \), multiply both sides by the reciprocal of \( \frac{3}{8} \), which is \( \frac{8}{3} \):

\[
x = -15 \times \frac{8}{3}
\]

4. Calculate the right-hand side:

\[
x = \frac{-15 \times 8}{3} = \frac{-120}{3} = -40
\]

Thus, the solution is:

\[
\boxed{-40}
\]