3X + 12 + X is equivalent to 4(3 + X). If we combine like terms in 3X + 12 + X, the reseult will be 4X + 12. If we use distributive property on 4(3 + X) , then we will get 12 + 4X. Using the communtative property of addition, both of the equations, 4X + 12 and 12 + 4X are the same.