Answer: 2 + 4d
Step-by-step explanation: In this problem, we're asked to simplify 2 + 3d + d. Notice that the 3rd term in this problem, d, has no coefficient. In this situation, we can give it a coefficient of 1.
Now, when simplifying this problem, it's important to understand that we can only combine like terms. Like terms are terms that have the same variables so we have 3d + 1d which is 4d. Since 2 has no like terms to combine with, it stays the same so we have 2 + 4d.
So our answer is 2 + 4d and we must stop here because these are not like terms since 2 does not have a variable.