6th grade math :) help me please!

Step-by-step explanation:

Identify the variable in each term. If two or more terms have the same variable, they are "like" terms.*

1) Like terms are found in selection b. They are 7r and r.

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2) The variables in selection d are u and y, not the same. Only unlike terms are found in selection d. (Selection b has variables x, b, x. The x-terms are like terms and can be combined.)

* Strictly speaking, it is the constellation of variables you want to match. For example, terms 3xy, 4xy², and -5x²y all have variables x and y, but the powers of those variables don't match from term to term. For terms to be "like", the variables and their powers need to match.

b. 153 students do not participate in sports and seventy-five 12th graders were surveyed