Let's denote the unknown number as \( x \).
According to the problem statement, we can model the situation with the following equation:
\[ 2(x + 7) = 3x \]
Now, let's solve for \( x \):
- Distribute the 2 on the left side of the equation:
\[ 2x + 14 = 3x \]
- Next, let's isolate \( x \) by subtracting \( 2x \) from both sides:
\[ 14 = 3x - 2x \]
This simplifies to:
\[ 14 = x \]
- Therefore, the value of the unknown number \( x \) is:
\[ x = 14 \]
In summary, the equation we created was:
\[ 2(x + 7) = 3x \]
After solving, we found that the missing number is:
\[ \boxed{14} \]