6d - e + 3d - 2e

(combine like terms)

6d and 3d are like terms, so you take them and add them together because they're both positive. You get 9d-e-2e. - e and - 2e are also like terms so you would put these together but subtract them to get 9d-3e.

Like terms are terms that have the same variable parts.

In your problem, 6d and 3d are like terms and can be combined.

-e and - 2e are like terms and can be combined.

6d - e + 3d - 2e =

= 6d + 3d - e - 2e

= 9d - 3e

Answer: 9d - 3e