Answer:
a) linear model is 
b) Amount earned by Samantha is $950.
Step-by-step explanation:
Given: Samantha base salary= $800
She get tips averaging 15% of the meals she serves.
Samantha serve meals worth a total of $1000.
Lets assume total worth of meal served by Samantha be "x".
And Total earning of samantha in a months be "y".
To calculate the total income of samantha, we need to add fixed income and variable income.
∴ 
(∵ Tip is 15%)
∴ 
Hence, the linear model for the total earning of samantha is
.
Now, finding the total amount earned by samantha.
As given, Samantha serves meals worth a total of $1000.
Subtituting the value of meals worth in the equation.

⇒
∴ y= $950
Hence, the total amount earned by Samantha is $950.