16. there are 4 terms, +4m, +3, +m, +1 +4m and +m are like terms, +3 and +1 are like terms. (Like terms can be combined, +4m+m=5m). the coefficient (the number to the right of a letter) for the term +4m is +4, the coefficient for the term +m is +1. +1 and +3 are the two constants. (constants are numbers without a letter)
I hope you can do the rest by yourself now. Note: in #18, 7j, 11jk, and k are not like terms. There are no like terms in number 18. Neither are there any like terms in #20
