It can be helpful to make sure the variables in each term are in alphabetical order. This makes it easier to see "like" terms. The variables in each term are ...
x^2 y z
y z^2
x^2 y z
y
Only the first and third terms are like terms, so those are the only ones that can be combined. Their coefficients are -7 and -1, so sum to -8. The combined term is of highest degree, so in standard form we list that term first.
