Factoring is the opposite of the distributive property of multiplication over addition. 12x+4 We look at the 12 and the 4 and think what their greatest common factor is. It is 4. So we factor out 4, then divide each 12 and 4 by 4 inside the parentheses: 4(3x+1) As a check we multiply it back out using the distributive property of multiplication over addition, and it goes back to 12x+4. Edwin