Find the number of non-negative integral solutions of `x+y+z+wlt=20.`

Explanation

To find the number of non-negative integral solutions to the equation \( x + y + z + w \leq 20 \), we can transform this inequality into an equation by introducing a new variable \( t \).

### Step-by-step Solution:

1. **Transform the Inequality**:
We can rewrite the inequality \( x + y + z + w \leq 20 \) as:
\[
x + y + z + w + t = 20
...