Respuesta :

Your awnser would be..... B. monomial
Like you said combine like terms.
You would first combine: 7x and 3x since addition comes first.
Your will get: 10x-x
Next: You would subtract x from 10x since that's all you have left to do.
Your answer would be: 7x, which is a monomial. 
HOPE THIS HELPS! ^_^