To factor the expression \(15s - 18t\), we need to find the greatest common factor (GCF) of the two terms.
The coefficients are 15 and 18. The GCF of 15 and 18 is 3.
Now we can factor out 3 from each term:
\[ 15s - 18t = 3(5s - 6t) \]
Thus, the factored form of \(15s - 18t\) is:
\[ 3(5s - 6t) \]
Here, \(3\) is the whole number greater than 1.