To model the situation, let's define the unknown number as \( x \). The equation based on the description provided is:
\[ 3x + 12 - 5x = 22 \]
Now, we will simplify and solve the equation:
- Combine like terms on the left side:
\[ (3x - 5x) + 12 = 22 \]
This simplifies to:
\[ -2x + 12 = 22 \]
- Next, subtract 12 from both sides:
\[ -2x + 12 - 12 = 22 - 12 \]
This simplifies to:
\[ -2x = 10 \]
- Now, we divide both sides by -2 to solve for \( x \):
\[ x = \frac{10}{-2} \]
This simplifies to:
\[ x = -5 \]
Therefore, the number is \( \boxed{-5} \).