9514 1404 393
Answer:
 a) 205x
 b) the total cost (in dollars) of adopting one dog
Step-by-step explanation:
a) The sum of costs for one dog is ...
 $90 +75 +40 = $205
Then the total of costs for x dogs will be ...
 205x . . . . the expression representing the cost to adopt x dogs
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b) The coefficient of x is the total cost of adopting one dog.