1. Let's understand what a common factor is: it is a number or expression that divides two or more terms without leaving a remainder. 2. To find a common factor in step 6, identify all terms in the expression you are working with. 3. Look for numbers and variables that appear in every term. 4. For example, if the terms are $6x$, $9x^2$, and $15x^3$, the coefficients are 6, 9, and 15, while the variable part is $x$, $x^2$, and $x^3$. 5. The greatest common factor (GCF) of the coefficients 6, 9, and 15 is 3. 6. The common variable factor is the lowest power of $x$, which is $x$. 7. Therefore, the common factor is $3x$. 8. We factor out $3x$ by dividing each term by $3x$: $6x \div 3x = 2$, $9x^2 \div 3x = 3x$, and $15x^3 \div 3x = 5x^2$. 9. The expression becomes $3x(2 + 3x + 5x^2)$. 10. This completes the factoring step, simplifying the expression and making it easier to work with further.